No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Mode of action of Hetrazan on filarial worms
... Key results in the field of drug development with the Litomosoides model include showing the microfilaricidal efficacy of diethylcarbamazine (DEC) in cotton rats , the lack of macrofilaricidal efficacy of DEC (Hawking et al. 1950), the loss of the microfilarial sheath following DEC treatment and co-localization of neutrophils and phagocytes with remaining MFs (Hawking et al. 1950;Schardein et al. 1968), the activity of ivermectin against developing stages (Campbell 1982), the suppression of microfilaremia by emodepside (Zahner et al. 2001), the macrofilaricidal activity of the benzimidazoles flubendazole (Zahner and Schares 1993;Hübner et al. 2019a) and oxfendazole , and the development of treatment strategies against Wolbachia (Hoerauf et al. 1999;Specht et al. 2018). ...
... Key results in the field of drug development with the Litomosoides model include showing the microfilaricidal efficacy of diethylcarbamazine (DEC) in cotton rats , the lack of macrofilaricidal efficacy of DEC (Hawking et al. 1950), the loss of the microfilarial sheath following DEC treatment and co-localization of neutrophils and phagocytes with remaining MFs (Hawking et al. 1950;Schardein et al. 1968), the activity of ivermectin against developing stages (Campbell 1982), the suppression of microfilaremia by emodepside (Zahner et al. 2001), the macrofilaricidal activity of the benzimidazoles flubendazole (Zahner and Schares 1993;Hübner et al. 2019a) and oxfendazole , and the development of treatment strategies against Wolbachia (Hoerauf et al. 1999;Specht et al. 2018). ...
Filariae are vector-borne parasitic nematodes that are endemic worldwide, in tropical and subtropical regions. Important human filariae spp. include Onchocerca volvulus, Wuchereria bancrofti and Brugia spp., and Loa loa and Mansonella spp. causing onchocerciasis (river blindness), lymphatic filariasis (lymphedema and hydrocele), loiasis (eye worm), and mansonelliasis, respectively. It is estimated that over 1 billion individuals live in endemic regions where filarial diseases are a public health concern contributing to significant disability adjusted life years (DALYs). Thus, efforts to control and eliminate filarial diseases were already launched by the WHO in the 1970s, especially against lymphatic filariasis and onchocerciasis, and are mainly based on mass drug administration (MDA) of microfilaricidal drugs (ivermectin, diethylcarbamazine, albendazole) to filarial endemic areas accompanied with vector control strategies with the goal to reduce the transmission. With the United Nations Sustainable Development Goals (SDGs), it was decided to eliminate transmission of onchocerciasis and stop lymphatic filariasis as a public health problem by 2030. It was also requested that novel drugs and treatment strategies be developed. Mouse models provide an important platform for anti-filarial drug research in a preclinical setting. This review presents an overview about the Litomosoides sigmodontis and Acanthocheilonema viteae filarial mouse models and their role in immunological research as well as preclinical studies about novel anti-filarial drugs and treatment strategies.
... In mice, it is absorbed and rapidly distributed, reaches the liver, kidney, adrenal glands, muscle, and gastrointestinal tract and accumulates in the brain in 20 min, and diminishes after one hour. 11 Metabolism of the drug is also very rapid and is excreted in four different forms, in all of which the piperazine ring remains intact no abortifacient or teratogenic effect is reported. 12 Certain reactions to treatment with DEC occur in persons infected with Bancroftian and Brugian filariasis. ...
The common filarial worm of cattle, , whose larvae are known as , are discovered in the blood and peritoneum and cause a condition known as cerebrospinal nematodiasis. There is an unavoidable need for prompt detection and treatment of these filarial diseases. Infections caused by a variety of filarial species have traditionally been treated with diethylcarbamazine (DEC). The most notable aspect of DEC is that, , it appears to have little effect on filarial parasites. However, DEC may act on the parasite's surface, unmasking antigen. This study was initiated to evaluate the effect of DEC on the antioxidant enzyme activities, Superoxide dismutase (SOD), and Catalase (CAT) of mice infected with (Mf).
was collected and the Mf was isolated and injected into Swiss-bred mice for 12 days. The animals were grouped as Control, Control +DEC, Control + Mf, and Control+Mf+DEC.
The results showed that CAT activity in the peritoneal fluid of Control+Mf+DEC was found to be elevated at a higher level compared to the control. The activity in the Control+DEC and Control+Mf mice showed similar values. SOD activity in the peritoneal fluid of Control+Mf+DEC mice remained elevated from the 1 day to the 12 day compared to the control. Though DEC alone treated mice did not show any profound increase in the activity of these enzymes. The rise in SOD level during the 3 and 5 day of the DEC-treated infected mice may be due to the production of active oxygen species. Proposed to occur as a result of a tilt in the biochemical balance of the cells towards the oxidative damage, failing which decreased removal of free radicals leading to tissue damage results.
The result showed that the DEC treatment may be affecting the survival of the Mf shown by the increased antioxidant enzymes which may be due to the inflammation caused by the excretory products of Mf.
... Intravenous DEC 5 produces a rapid (within minutes) decline in the level of microfilariae found circulating in the blood and a partial killing of the adults 21 . This rapid effect of DEC leads to the entrapment of the microfilariae and the adults in the liver, lymph nodes, and lungs where they undergo attack by the mononuclear phagocyte system (MPS) and lysis 22,23 . The reduction in circulating parasites is, however, transient in nature, and lasts several hours before returning to former levels. ...
Diethylcarbamazine is an important classic drug used for prevention and treatment of lymphatic filariasis and loiasis, diseases caused by filarial nematodes. Despite many studies, its site of action has not been established. Until now, the consensus has been that diethylcarbamazine works by activating host immune systems, not by a direct action on the parasites. Here we show that low concentrations of diethylcarbamazine have direct and rapid (<30 s) temporary spastic paralyzing effects on the parasites that lasts around 4 h, which is produced by diethylcarbamazine opening TRP channels in muscle of Brugia malayi involving TRP-2 (TRPC-like channel subunits). GON-2 and CED-11, TRPM-like channel subunits, also contributed to diethylcarbamazine responses. Opening of these TRP channels produces contraction and subsequent activation of calcium-dependent SLO-1K channels. Recovery from the temporary paralysis is consistent with inactivation of TRP channels. Our observations elucidate mechanisms for the rapid onset and short-lasting therapeutic actions of diethylcarbamazine.
... Dans les filarioses expérimentales à microfilarémie non périodique, cette action n'est pas retrouvée, même chez celles dont les microfilaires sont détruites par la DEC. C'est le cas de L itom osoides carinii parasite de Sigm odon hispidus (Hawking et al., 1950) ou de Brugia pahangi chez le chat (Denham et al., 1971). ...
... DEC, administrated in the form of a water-soluble citrate salt (DEC-CIT, HETRAZAN®), has been applied almost exclusively to treat filarial nematodes since the early 1950s. 4,5 A single dose of this drug reduces microfilaremia over the course of one year. 2,3 Mass drug administration programs have been successful in reducing microfilaremia and providing important collateral deworming benefits. ...
Diethylcarbamazine, administered as a water-soluble citrate salt, has been used for more than 50 years as the first-line drug in the treatment of lymphatic filariasis. Mass drug administration programs have been successful in reducing microfilaremia and providing important collateral deworming benefits. One of these initiatives is based on the addition of diethylcarbamazine citrate to table salt. The fortified salt retaining the efficacy of the drug in reducing microfilaremia, but there is little information about its behavior above room temperature. In this study, the thermal stability of diethylcarbamazine, as a free base and a citrate salt, was investigated by differential scanning calorimetry and thermogravimetry under different conditions. Diethylcarbamazine does not release hazardous degradation substances above its melting point. It was also confirmed that this drug is stable at normal cooking temperatures, even when dry heat cooking methods, such as baking or grilling, are considered. However, if the drug is formulated as a salt, as in the case of the citrate, special attention needs to be given to the degradation substances of the counter ion.
... Later, Santiago-Stevenson et al. (1947) [2] showed that this compound was effective in the treatment of Wuchereria bancrofti infection in humans. Hawking et al. (1950) [3] proposed the action mechanism of DEC. Since the extensive studies by Kessel (1957) [4] and his colleagues, the drug's strong filaricidal activity with few side reactions has been widely recognized and accepted. ...
... It may be possible that piperazine compounds also alter the surface of microfilariae resulting into enhanced cellular adherence to them. Exposure of antigenic determinant sites on the surface of microfilariae by DEC makes them more vulnerable to immune attack (Hawking et al., 1950;Piessens and Beldekas, 1976). ...
Enhancement of in vitro cellular adherence to microfilariae (mf) has been regarded as an important phenomenon in microfilaricidal action of diethylcarbamazine. Modulation of in vitro cell-adherence to sheathed (Brugia malayi and Litomosoides carinii) and unsheathed (Acanthocheilonema viteae) mf by various antifilarials has been investigated using splenocytes from naive mastomys and cotton rats (Sigmodon hispidus). All the piperazine derivatives (diethylcarbamazine, Centperazine, N-oxide a major metabolite of DEC) enhanced antibody-mediated cell-adherence to both sheathed and unsheathed mf in vitro but not levamisole, a compound with a different chemical structure. Among all piperazines, maximum promotion of cell-adherence was exerted by N-oxide followed by Centperazine (a piperazine compound synthesised in our Institute) and DEC in that order. Sheathed mf of B. malayi and L. carinii required complement and specific IgG antibody (from rabbit immunized with specific antigens) while cell-adhesion was complement independent in case of unsheathed mf of A. viteae requiring specific IgM antibody (from infected mastomys). Maximum adherence occurred in presence of 90-120 days old infected serum whether microfilariae were isolated from blood or uteri of female worm, however, adhesion was comparatively very low in latter case. Intensity of cells adhered was proportional to percent mf showing cell-adherence. Cell adherence decreased with increasing dilution of antibody
... When placed in an electric current, some nematodes show an electrotaxis (or galvanotaxis), accmnulating at one electrode or the other (1,2,3,17). Accumulation is usually at the cathode (l, 2, 8, 1 l, 14), though not always (3,9,17). While electrotaxes have been reported from a variety of nematodes, the phenomenon has not been examined in Caenorhabditis elegans, despite the wide use of that species as a hehavioural model (4,5,16). ...
C. elegans responds directionally to a DC current. The response may be to the anode or cathode, depending on the current, potential difference, and ion concentration of KC1, Tracks of the responding nematodes show that electrotaxes are genuine orientation phenomena. The directional movement is not due to the passive movement of nematodes or to the influence of currents on the muscular physiology; electrotaxes are mediated sensorily. Details of the response are described.
... In fact, after 15 days of treatment patients M and N, receiving 10 and 0 3 ,ug/hour during the day, had the same number of MFAC as before treatment. It is known that the destruction of MFS is brought about by host cells (Hawking et al., 1950), so the rather poor and variable effect of DEC against MFS in the anterior chamber may possibly be ascribed to the low cellular content of the normal aqueous. It is of interest that DEC can, however, benefit onchocercal iritis, in which the cellular content of the aqueous is greatly elevated (Anderson et al., 1976a). ...
Diethylcarbamazine was given as eye drops in varying concentrations in a half-log dilution series from 1.0 to 0.0001% to patients with ocular onchocerciasis. Migration of microfilariae into the cornea, followed by their straightening and disintegration, was observed with delivery rates as low as 0.1 microgram/hour. Dose-related adverse inflammatory reactions, including the development of globular limbal infiltrates with itching and redness, were seen with delivery rates as low as 0.6 microgram/hour, but substantial inflammatory reactions, including severe vasculitis, were seen only with delivery rates of or above 1.0 microgram/hour. This suggests that it should be possible to achieve beneficial clearing of the microfilarial load, without adverse reactions, by continuous non-pulsed delivery of the drug. Technology exists for such delivery, either directly into the eye or systemically by a transdermal system that could give 3 to 7 days' treatment from each application. The observations reported suggest that after preliminary clearing of the microfilarial load by carefully controlled delivery of DEC it may be possible to maintain therapy by less strictly controlled delivery in DEC-medicated salt, or to use treatment with suramin, without incurring substantial adverse reactions, such as a deterioration in vision in cases in which the optic nerve is already compromised. Continuous non-pulsed DEC delivery systems could have a place in the management of onchocercal sclerosing keratitis. The unique opportunities for using the ocular model to define the requirements for beneficial non-damaging therapy with DEC should be explored in further field trials.
The filarial parasite, Loa loa, causes chronic infection in an estimated 10 million people living in Central and West Africa and in long-term visitors to endemic areas. Although generally perceived as a relatively benign infection, the symptoms of loiasis can be disabling and infection has been associated with excess mortality and rare but serious complications of infection-associated eosinophilia. Treatment of loiasis is complex, due to potentially severe complications associated with microfilarial killing, especially in patients with high-microfilarial loads, and incomplete efficacy of macrofilaricidal therapies. In the following chapter, currently available therapies for loiasis and their use in the treatment of loiasis are reviewed. Novel therapies and adjunct measures are also discussed. Finally, a simple stepwise approach to treatment is suggested.
Elephantiasis is the most severe and dramatic complication of lymphatic filariasis (LF), a chronic infection caused primarily by the filarial parasite Wuchereria bancrofti . Dracunculiasis is another chronic infection caused by a filaria‐like parasite, Dracunculus medinensis , also known as the guinea worm. This chapter considers LF and dracunculiasis, while onchocerciasis, another filarial infection, and discusses together with trachoma as major causes of blindness. The health and socioeconomic impact of LF for the poorest people of India, Africa, and elsewhere is huge. A number of factors, both biological and social, provide great optimism that LF elimination efforts through mass drug administration could be extended worldwide. Podoconiosis is another type of lymphedema found in the tropics, and bears some clinical resemblance to elephantiasis caused by LF. The control of LF and guinea worm infection, like so many neglected tropical diseases control programs, represents extremely low‐cost and cost‐efficient measures.
Der Befall mit Helminthen gehört nach wie vor zu den aktuellen Problemen der Medizin. Auch in unseren Breiten werden bei genauen Erhebungen an vielen Orten immer noch beträchtliche Verwurmungen, insbesondere von Kindern, festgestellt. Dies gilt durchaus nicht nur für den Befall mit Enterobius vermicularis, der nach Sommerfeld (1958), Dieckhoff (1961), Pbiebe (1961), Sommer (1961) u. a. bei etwa 70–80% der untersuchten Kinder gefunden wird, sondern auch für andere „einheimische“ Helminthen. So zeigt die einer Veröffentlichung von Martisching (1960) entnommene Tab. 1, daß außer mit Enterobiasis gebietsweise auch mit dem häufigen Vorkommen von Spulwurm- und Peitschenwurm-infektionen gerechnet werden muß.
Schon in unserem gemäßigten Klima und in normalen Zeiten kommt den Helminthen vielerorts eine Bedeutung als Krankheitserreger oder Plagegeister zu, die nicht unterschätzt werden darf. In der nebenstehenden Tabelle 1 sind Befallsziffern für Spulwürmer aus verschiedenen Gebieten Deutschlands und einiger Nachbarländer zusammengestellt, die die von Gebiet zu Gebiet stark wechselnde Häufigkeit dieser Parasiten erkennen lassen. Bei der Auswahl der Statistiken wurden nur die letzten 15 Jahre berücksichtigt. Im Gefolge des vergangenen, wie schon des ersten Weltkrieges hat die Häufigkeit und Stärke der Spulwurminfektionen in manchen Gebieten, namentlich West- und Süddeutschlands erheblich zugenommen (siehe z. B. die Befallsziffern in Tübingen auf der Tabelle). Diese Zunahme kommt auch deutlich in der Häufung klinischer Mitteilungen in den Nachkriegsjahren über schwere und tödliche Ascaris-Infektionen mit Darm- und Gallengangskomplikationen zum Ausdruck. In Darmstadt und Umgebung erreichte der Spulwurmbefall durch besondere Umstände eine Höhe wie sonst nur in warmen Ländern. Anfang 1947 hatte dort Burlingame (1949) bei 84% von 1161 Kindern und bei 70% von 247 Erwachsenen Ascaris-Eier gefunden. 1948 war nach Schlieper und Kalies (1949) die Bevölkerung Darmstadts zu 52% mit Ascaris infiziert, die des benachbarten Griesheims sogar zu 90%, wobei sich in diesem Zentrum des Gemüsebaues auf Grund von Eizählungen im Stuhl eine Befallsstärke von im Mittel 45 Würmern je Person errechnen ließ.
Forty-four patients with onchocerciasis who were treated with diethylcarbamazine (DEC) were entered into a double-blind study using prednisone or placebo to try to alleviate the reactions to treatment. Prednisone was given in an initial dose of 20 mg t.i.d. starting the day before DEC and was decreased stepwise over the next week. The reactions to treatment were quantitated using a recently described scoring system.The mean (±S.D.) microfilarial count in the placebo group prior to treatment was 279 ± 177·6 and in the prednisone group was 283±222±6. Prednisone produced a significant reduction in the severity of the reaction to treatment with DEC, the peak mean score being 88 in the placebo group and 25 in the prednisone group. Prednisone almost completely abolished the cardiovascular and glandular components of the reaction but pruritus was not prevented and the skin rash still occurred although it appeared later than in the control group.Prednisone also significantly reduced the effectiveness of DEC. In the placebo group, the mean microfilarial count one week after stopping DEC was reduced by 94·8% compared to the initial value while in the prednisone group it was reduced by only 79·8% of the control value. Further studies are in progress to find the optimum dose of prednisone which will alleviate the reactions to treatment without reducing the effect of DEC.
Thirty-eight patients with onchocerciasis who were treated with diethylcarbamazine (DEC) were entered into one of two randomized double-blind studies using indomethacin or cyproheptadine, or their matching placebos, in order to try to alleviate the reactions to treatment. Twenty patients received cyproheptadine (or placebo) in a dose of 4 mg three times daily for eight days, starting one day prior to DEC therapy. The remaining patients received indomethacin, 25 mg (or placebo) two capsules initially and then four further doses of 25 mg over the next 36 hours. The reactions to treatment were quantified using a recently described scoring system.DEC reduced the microfilarial skin snip count by 96–98% in all treatment groups and treatment with indomethacin or cyproheptadine did not interfere with the microfilaricidal action of DEC.Neither cyproheptadine nor indomethacin apparently reduced the severity of the reactions following the use of DEC in patients with onchocerciasis. We conclude that release of prostaglandins, histamine and serotonin are not primarily involved in the production of the Mazzotti reaction.
Although the immune response to helminth infection is, as far as is known, comparable to that stimulated by any other type of infective agent, the antigenic complexity of the helminths, their varied and at times extended developmental cycles, and the differing locations which they inhabit in the body imply that a very wide range of responses can be expected. Experimental studies have confirmed that acquired resistance to helminth infections is dependent on specific immune responses; this includes the proliferation of thymic and bursalequivalent lymphocytes and the production of mediators of cellular responses and/or immunoglobuhns, respectively. The proportionate quantitative and qualitative contribution of each to protective immunity varies considerably for each parasitic helminth infection. A substantial proportion of the immune response appears unrelated to protective immunity, as there is increasing evidence being obtained for an immunopathological role.
The purpose of this chapter is to describe biochemical or physiological events observed in nematodes exposed to an anthelmintic. Whether these pharmacologically mediated events truly represent a mode of action is difficult to prove, and the action described may represent a secondary event unrelated to the mode of action or it may be part of a series of events involved in the killing process.
While the physiological roles of eosinophils have long been debated, recent studies on the mechanism of action of the antifilarial drug diethylcarbamazine (DEC) provided unexpected insights on their connections to other innate immunity effector cells. DEC has been successfully used for many decades as treatment and prophylaxis of filariasis, and more recently proven effective for Tropical Pulmonary Eosinophilia, but little understanding of its mechanisms of action in either condition exists. DEC was also used as an inhibitor of leukotriene production, until more selective blockers of the 5-lipoxygenase (5-LO) appeared. DEC is beneficial in some asthmatic patients, but the relationship of this effect to the suppression of leukotriene production remains unexplored. Evidence from other groups that DEC suppresses microfilaremia in mice through a mechanism requiring the inducible isoform of NO synthase (iNOS) prompted us to reexamine its effects in a murine model of asthma, since infiltrating eosinophils are a major component of infiltrates in this disease, and because NO is believed to effectively modulate histological and functional changes in asthma. DEC suppressed allergic pulmonary inflammation in mice by a combination effects on both the lungs and the bone-marrow. Its primary hemopoietic effect required induction of apoptosis during eosinophil differentiation, leading to decreased circulating and infiltrating eosinophil numbers. However, pulmonary neutrophil infiltrates were also markedly reduced, even though DEC lacked a suppressive effect on neutropoiesis. Eosinopoiesis was downmodulated in a way strictly dependent on both iNOS and the endogenous ligand for the CD95 death receptor, CD95L. This process is effectively blocked by cysteinyl-leukotrienes, which are important mediators in asthma. The mechanism for DEC effects in experimental asthma, therefore, seems to be dual: a) induction of NO- and CD95L-dependent apoptosis in immature eosinophils; b) blockade of leukotriene production, which would, if unabated, protect eosinophils from iNOS-CD95L-dependent apoptosis. We further examined the coordinated regulation of eosinophil and neutrophil infiltrates, which was suggested by observations in DEC-treated allergic mice, and evaluated whether the 5-LO pathway plays a role in this phenomenon. This was done in a model of eosinophil migration to the peritoneal cavity induced by the eosinophil chemoattractant, eotaxin (CCL11). In nonallergic mice, eotaxin induced eosinophil accumulation, followed by both neutrophil and mononuclear phagocyte recruitment. 5-LO was required for recruitment of both neutrophils and mononuclear phagocytes by eotaxin to the peritoneal cavity. Recruitment was dependent on eosinophils, as shown by transfer experiments using eosinophil-null recipients. Together, these observations unveil hitherto undescribed connections between eosinophil and neutrophil populations, which are dependent on 5-LO and regulated by DEC, and provide a setting in which eosinophils may contribute to host antimicrobial defense by their ability to recruit other effector cell populations.
Diethylcarbamazine (DEC) interferes with cyclooxygenase and lipoxygenase pathways, reducing the production of thromboxane, prostacyclin, prostaglandin and leukotrienes. Recent studies using different experimental models of inflammation have indicated that DEC, in addition to inhibiting cyclooxygenase and lipoxygenase pathways, also inhibits nuclear transcription factor kappa B (NF-κB) activation, which is a key regulator of proinflammatory genes such as TNF-α, IL-1β, inducible nitric oxide synthase (iNOS) and even cyclooxygenase 2 (COX-2). The aim of the present study is to provide a comprehensive summary of DEC, including a description of filaricidal action, inhibition of synthesis and secretory pathways, immunomodulatory activity, and specific inhibition of lipoxygenase and cyclooxygenase pathways.
A characteristic of filarial diseases is the presence of eosinophil leucocytes. The functions of this granulocyte in both parasite killing and suppression of inflammation, the apparently paradoxical roles currently suggested, are well exemplified by filarial diseases where both anaphylactoid manifestations and destruction of parasites occur. The blood and tissue eosinophilias found in filarial diseases are discussed, and particular attention is drawn to the location of eosinophils in infected tissues. These cells are commonly found in two locations, perivascular sites proximal to the parasites themselves. Eosinophils are found in close proximity to microfilariae particularly after administration of antimicrofilarial drugs; in contrast, prior to administration of the drug the parasites often lie free of cells. In vitro systems for studying the interactions between host cells, serum and filariae have shown that relatively few individuals in an infected population possess detectable antibodies directed against surface antigens of microfilariae, and that repeated infection is probably required to ensure the presence of circulating antibodies directed against surface determinants on infective larvae. The in vitro killing of microfilariae by granulocytes and immune serum is enhanced by the presence of fresh complement. The antifilarial drug diethylcarbamazine appears to have a significant effect on this in vitro system increasing the rate of adherence of granulocytes and the rate of killing of microfilariae. Interestingly, this drug has a direct effect on the granulocytes inducing apparently selective degranulation of eosinophils; this effect can be blocked by theophylline.
Diethylcarbamazine (DEC) interferes with arachidonic acid metabolism for the clearance of microfilariae in Wuchereria bancrofti infected individuals. In this study, we have quantified the plasma concentrations of prostaglandin E2 (PGE2) and 6-keto-PGF1α, the end products of arachidonic acid metabolic pathway in microfilaraemics (DEC treated and untreated), and normal healthy individuals at pre- and 3,9,12,36, and 72 h of post-DEC treatment. We have also determined the microfilariae counts at pre and post day 2 (36 h) and day 3 (72 h) of DEC treatment by membrane filtration technique. Significant reduction in PGE2 and 6-keto-PGF1α concentrations was found at 12 h of DEC treatment. Rapid reduction in microfilarial counts was observed at 36 h of post-DEC treatment. Higher levels of prostaglandins were found at pre-treatment hours in microfilaraemics compared to normal healthy individuals (P < 0.05). Our findings indicate that DEC inhibits prostaglandins for the clearance of microfilariae, and increased levels of prostaglandins in microfilaraemics may be contributed by the parasite or host upon stimulation.
The primary physiological mode of action of nearly all drugs used to control helminth parasites is not well understood. Examination of the general modes of action in terms of parasite requirements for survival may, however, provide guidelines to continue our present investigations and direct us for future research.
Two general areas of drug activity are (1) interference with energy‐generating metabolism, and (2) interference with proper neuromuscular coordination. Few exceptions are found to these areas because the target organisms require little else for survival.
The target of most previously effective and many presently effective anthelmintics is an adult parasite. Adult helminth parasites must maintain an advantageous feeding site and must transport and metabolize substrates (primarily glucose) to generate life‐maintaining energy. Adult worms have almost no other short‐term requirements for survival because they have little or no metabolic activity in either lipid synthesis or oxidation, nucleic acid synthesis, or protein synthesis (except egg‐laying).
Examination of specifics of energy‐generating metabolism and putative neurochemical transmitters allows us certain predictions in relating a given drug activity to an individual species. These examinations indicate that such diversity exists among helminth metabolic or nervous systems that a broad‐spectrum anthelmintic would most likely inhibit at several sensitive points.
Published information on drug action and differences in data interpretation are discussed. Two novel areas for future anthelmintic investigations may be (1) juvenile hormone or ecdysone analogs, and (2) pheromones. A combined empirical and rational approach to the development of new drugs may be the most efficient avenue of future research.
Summary The treatment of patients with onchocerciasis with diethylcarbamazine (DEC) can produce local or systemic reactions within a few hours—the Mazzotti reaction. In order to study the immunological mechanisms which could underly this reaction, three patients were studied who were undergoing treatment, and two normal subjects who had been treated successfully previously were controls. Blood eosinophils were vacuolated and a higher proportion than normal had Fc receptors. After taking 50 mg DEC orally, in parallel with the development of symptoms in the three patients, localised in two and generalized in one, there was a fall in blood eosinophil counts which were lowest at 12 h. Serum IgG levels fell slightly in all three patients, and the serum IgE level fell in one, but there were no changes in the titres of antimicrofilarial antibodies. Levels of circulating immune complexes were not elevated at any time, and complement levels did not alter during the reaction. From these findings and a review of previous work on the mechanisms of the Mazzotti reaction it is suggested that when microfilarae are damaged by DEC, an inflammatory reaction is produced which may be localised or generalized. The reaction does not appear to require the generation of circulating immune complexes, or systemic complement activation, even when the reaction is generalized. It is suggested that the clinical features of the reaction may be due to the effects of mediators secreted from inflammatory cells including eosinophils, in sites where microfilarae are being destroyed.
Culture-derivedLitomosoides carinii microfilariae (MFF) were used in in vitro and in vivo systems to investigate the effect of diethylcar-bamazine (DEC) on these MFF. In vivo: Male rats,Mastomys natalensis, all of the same age, were injected intrathoracically (12) or intraperitoneally (36) with 103 or 104 MFF. After 30 min one half of each group of rats was given DEC per os. At 30, 60, and 120 min after DEC administration, two rats from the treated and two from the untreated group were bled and killed. The pleural or peritoneal cavities were rinsed with warm saline (0.15m NaCl) to recover MFF. In both the intrathoracic and intraperitoneal experiments, equal numbers of MFF were recovered from treated and control rats at 30 and 120 min. However, at 60 min 85.5% fewer were recovered from the treated than from the nontreated animals. MFF were not found in the blood. In vitro: MFF were added to tissue culture dish wells (Linbro Div., Flow Labs, Hamden, Conn) prepared as follows: DEC-Serum (serum from normal rats given DEC at 500 mg/kg), DEC+Serum (serum with added DEC), serum only, RPMI 1640 only, and RPMI 1640+DEC. Furthermore, the five treatments were prepared either with or without unstimulated peritoneal exudate (PE) cells. At 30 min in the DEC-Serum wells 45% of the MFF had adherent PE cells; in the remaining wells these cells adhered to 11% or fewer MFF. We interpret the aforementioned phenomena as representing the first step in the trapping and elimination of MFF after DEC treatment ofL. carinii-infectedM. natalensis.
Other researchers have found that diethylcarbamazine (DEC) is effective treatment for filariasis despite a lack of demonstrated in vitro antifilarial activity. The results of our previous investigations using feline and murine leukemia virus models encouraged us to investigate the use of DEC with other infections. In our current experiments, DEC treatment was associated with lower brain fungal burden in fluconazole-treated mice following intravenous injection of Aspergillus fumigatus or increasing numbers of Cryptococcus neoformans organisms, and lower brain and kidney levels of Candida albicans following intravenous injection of increasing numbers of C. albicans. Further investigation of combined DEC and fluconazole treatment of fungal infections is warranted.
1.1. A Sardinian strain of Dirofilaria repens has been maintained in the laboratory for 6 years during which time 13 dogs have been infected during 3 passages. 1.1.a. The microfilariae of D. repens show periodicity, the maximum count in the peripheral blood occurring about midnight and the minimum about mid-day; the minimum number is about 20–40 % of the maximum.1.2.b. The microfilariae develop readily in Anopheles stephensi, less regularly in A. maculipennis atroparvus, and moderately well in Aëdes aegypti.1.3.c. Eighteen dogs were inoculated with infective larvae and 13 became infected. Only about 5% of the original infective larvae survived and were recovered as adult worms from the dogs which ultimately showed microfilariae.1.4.d. The prepaient period (before microfilariae were found in the blood) was about 26 weeks; the patent period lasted from about 17 months to over 3 years.1.5.e. Worms which had been 43 months in one dog were removed and implanted under the skin of two other dogs. Microfilariae appeared in the blood of the two recipient dogs after 5–6 days, and increased progressively in number. From their rate of increase it could be calculated that on the average each worm produced about 5,000 microfilariae per day.2.2. A Chinese strain of D. immitis has been similarly maintained for 3 years. 2.1.a. The microfilariae show periodicity, with a maximum about 6 pm and a minimum about 6 am; the minimum count is about 5–20% of the maximum.2.2.b. Development of the larvae was poor in most of the mosquitoes studied. Some infective larvae were found in A. aegypti and A. albopictus; partial development was found in A. cantons and A. atroparvus; little or no development took place in A. stephensi and A. gambiae.2.3.c. The prepaient period was about 32 weeks; the patent period is longer than 2 years.2.4.d. In one dog, there were no demonstrable microfilariae in the blood during the four months before death, although at autopsy the right ventricle contained 2 male D. immitis and 9 female ones, some of which were extruding living microfilariae.3.3. No pathogenic effects have been observed with either of these strains.
Previous investigations have revealed that in vivo use of diethylcarbamazine (N,N-diethyl-4-methyl-1-piperazine carboxamide; DEC), the mainstay of prevention and therapy for filariases, results in increased titers of antibody to feline oncornavirus-associated cell membrane antigen (FOCMA) in feline leukemia virus (FeLV)-infected cats.In the present study, the effect of in vitro DEC on detection of serum antibodies to retroviruses was investigated. The addition of DEC (5 mg ml−1, pH 7·3–7·4) to the serum diluent resulted in detection of antibody to FOCMA by indirect membrane immunofluorescence in five of five FeLV-infected cats, whereas samples from all five cats tested negative without the addition of DEC. In vitro DEC also increased the absorbance values generated by enzyme immunoassay human immunodeficiency virus type 1 (HIV-1) antibody testing of samples from (a) persons with AIDS-related disease; (b) persons with helper T-lymphocytes < 500 mm−3 blood; and (c) persons testing positive for antibody to HIV-1 env- but not gag-related antigens as determined by radioimmunoprecipitation and sodium dodecyl sulfate polyacrylamide gel electrophoresis (). We conclude that in vitro as well as in vivo use of DEC may alter results of antibody testing for retroviruses.
The immunopathogenesis of the anaphylactoid Mazzotti reactions has been studied by comparing physiologic and immunologic aspects of diethylcarbamazine-induced shock in Dirofilaria immitis infected dogs with antigen induced anaphylaxis in infected and uninfected controls. Filarial antigen, specific host IgG antibody, and C1 and C3 complement levels were quantitatively measured over time in relation to the levels of histamine and prostaglandin D2 in the blood and changes in mean blood pressure. D. immitis antigen injected into uninfected dogs having no detectable IgG antibody to D. immitis or Toxocara canis produced a rapid drop in blood pressure that paralleled a drop in C1 and C3 levels and an increase in prostaglandin D2. Antigen injected into infected dogs with IgG antibody produced a similar drop in blood pressure and complement and increase in prostaglandin D2 which differed from the uninfected group only in the slower clearance of antigen from the blood. Diethylcarbamazine alone produced no measurable changes in blood pressure or complement in uninfected hosts. Diethylcarbamazine, however, administered into skin test positive infected dogs, produced a temporally slower but quantitatively similar loss in blood pressure, drop in complement, and increase in prostaglandin D2 and histamine to that induced by antigen injection. Complement activation and immune complex formation are initiated by antigen release, and subsequent vasoactive mediator release leads to shock with prostaglandin D2 being quantitatively higher in blood than is histamine.
1.1. The literature dealing with the effects of anthelmintics on nematode metabolism is summarized.2.2. The compounds which are reviewed are: haloxon, metriphonate, crufomate, naphthalophos, phenothiazine, thiabendazole, parbendazole, tetramisole hydrochloride, bephenium hydroxynaphthoate, theium closylate, pyrvinium pamoate, dithiazanine iodide, methylridine, pyrantel tartrate, piperazine, and diethylcarbamazin.3.3. Some of the effects of these drugs on nematode metabolism are discussed.
Although diethylcarbamazine citrate (DEC) is successful drug in eliminating human filariasis, yet, its mode of action is still debatable. Herein, the effect of DEC to treat albino rats infected with the animal filarial parasite Setaria equina was tested. Microfilarial (mf) counts and sections from liver, lung, kidney as well as spleen were investigated at different time points after treatment by light microscopy. After 45 and 300min of treatment, a significant decrease in blood mf was observed accompanied by adherence of degenerated mf to both kupffer cells and leukocyte in liver sections. In lung sections, loss of sheath was observed at 45min, while degeneration was observed at later time points. In kidney sections, more mf counts and less matrix were observed in the glomeruli at all time points after treatment. Degenerated mf were observed in spleen sections only at, late time point, 480min after treatment. In conclusion, one of the possible mechanisms by which DEC reduces blood microfilarial count is trapping larvae in organs and killing them through cellular adherence.
Os autores realizaram uma ampla revisão sobre o tratamento da filariose bancroftiana com a droga dietilcarbamazina. Os aspectos interessantes sobre o histórico de sua descoberta e os conceitos básicos de sua farmacologia foram relatados de forma resumida. Ênfase especial, por outro lado, foi dada às especulações feitas pelos diversos autores sobre os achados intrigantes descritos na literatura. Foram trazidos os novos avanços sobre o conhecimento da doença, como por exemplo, a visualização pela ultra-sonografia do verme vivo de Wuchereria bancrofti, no seu hospedeiro natural, o homem. Isso possibilitou a compreensão de muitos dos achados aparentemente paradoxais encontrados na literatura sobre o tratamento da infeção com a DEC. Assim, devido à inexistência de uma droga sucessora que reunisse efeitos micro e macrofilaricidas ideais e aos novos conhecimentos sobre a bancroftose e sobre a própria dietilcarbamazina, foi-lhe conferido um novo realce. Esses aspectos a colocaram numa posição de destaque no cenário da infecção, à época do seu quase cinqüentenário de existência.
This chapter discusses the diethylcarbamatine and new compounds for the treatment of filariasis. Diethylcarbamazine is 1-diethylcarbamyl-4-methylpiperazine; it is also known as Hetrazan, Banocide, Notézine, Caricide, Carbilazine, Supatonin, and R.P. 3799. It was first put out as the chloride, but is now issued as the dihydrogen citrate, which contains only half its weight as base. In reports, it should be indicated whether the doses refer to a specific salt or to the base; unless otherwise stated, it can usually be assumed that the dose refers to the citrate. Diethylcarbamazine is a white powder, freely soluble in water, and has a slightly unpleasant sweetish taste. It is stable under all ordinary laboratory conditions. Furthermore, it is fully stable to autoclaving, even if mixed with diet (simulating cooking procedure). When diethylcarbamazine is given by mouth to either animals or man, it is rapidly absorbed from the alimentary canal. One dose of 10 mg base/kg produces a peak blood level of 4–5 μg/ml in 3 hours (when toxic symptoms are most prominent); the level gradually falls to zero within about 48 hours. Most of the excretion in the urine occurs in the first 24 hours during which time 10–26% of the dose may be recovered as diethylcarbamazine.
Treatment with the antifilarial drug diethylcarbamazine (DEC) results in a rapid decline in the number of microfilariae circulating in the blood of infected hosts. DEC induces morphological changes in the surface layers of microfilariae, but these alterations alone are probably insufficient to cause the death of the parasite, because the drug fails to reduce microfilaraemia in animals lacking filarial antibodies, and also does not shorten the survival of microfilariae in vitro. The effect of DEC in vivo is thought to result from the trapping of microfilariae in the liver, where they undergo lysis.
23 anthelmintics were tested against Brugia pahangi microfilariae and infective larvae in vitro and in Aedes aegypti infected with B. pahangi and jirds (Meriones unguiculatus) infected with a B. pahangi/patei hybrid. There was little correlation between the results obtained in vitro and in infected insects and the results obtained in these tests gave no indication of the activity in jirds. Three of the
compounds were macrofilaricidal in jirds and these were tested in cats infected with B. pahangi. One of these—5-benzamido-2(4-thiazolyl)-benzimidazole—was macrofilaricidal in cats and it is suggested that it should be
tested in other filarial systems.
It is concluded that the insect and in vitro tests are not good primary screens for filaricidal activity.
In the vast field of medical sciences, parasitology constitutes a small segment and has received comparatively scant attention, though worm infestation is a medical and public health problem of great magnitude, both in man and domesticated animals. The economic loss in terms of morbidity in man, loss of man-hours of work, and poor quality of animals, is exorbitant. Increasing the areas under cultivation, and quick and extensive modern transport system has contributed to the spread of worm infection beyond its traditional tropical and sub-tropical habitat. Drugs used as anthelmintics prior to World War II were mostly developed on empirical basis. Advances in the knowledge of physiology and biochemistry of parasites in last few years, have helped to a certain extent, in understanding the mechanism of action of known drugs, and development of newer chemotherapeutic agents. Understanding the mechanisms of action of anthelmintics, requires a more complete understanding of helminth physiology, biochemistry, effect of environment, and role played by immunological processes in parasitic diseases, than is available at present.
Nine Nigerians with severe onchocerciasis who were treated with diethylcarbamazine developed clinical changes, ranging in severity from mild itching to distress, cough, and syncope. Physiological changes (fever, tachypnoea, tachycardia, or hypotension) were seen in eight. In five patients the systolic blood pressure fell by more than 25 mm Hg, and one patient collapsed on attempting to sit up. Circulating eosinophils decreased profoundly in all cases, reaching their lowest levels just before or during the clinical and physiological changes. A fall in serum complement (c3) accompanied the reaction but there was no fall in antibody titre. Diethylcarbamazine probably acts on the parasite's cuticle, thus exposing it to the body's defence mechansims. The reaction coincides with the death of microfilariae, and the accompanying physiological changes may be so severe, even in generally healthy patients, the treatment should perferably be started in hospital.
Anti-parasitic drugs may achieve their therapeutic effect either by direct activity against the pathogenic organism, or by altering host factors which lead to parasite killing. In this review, we discuss the evidence for an indirect mode of action for one major anti-filarial drug, diethylcarbamazine (DEC). The interpretation most consistent with existing data is that DEC alters arachidonic acid metabolism in microfilariae and in host endothelial cells. These changes may result in vasoconstriction and amplified endothelial adhesion leading to immobilization of microfilarial parasites, enhanced adherence and cytotoxic activity by host platelets and granulocytes. These events would represent activation of the innate, non-specific immune system, independent of the adaptive, antigen-specific, immune response. This model explains the paradox between rapid clearance in vivo and the lack of an in vitro effect, as well as the efficacy of DEC in non-immune animals. It may also account for the inconsistencies in the effects of DEC against different filariae in different host species. In addition, we discuss the significant side-effects often associated with treatment of heavily infected patients, and the longer-term changes in T-cell reactivity and the host-parasite relationship which follow successful treatment with DEC.
The direct action of diethylcarbamazine (DEC) on the infective larvae of Brugia pahangi was studied. The larvae were cultured in RPMI 1640 supplemented with foetal bovine serum and antibiotics for 22 days. Most of the larvae remained alive for 8 days, but survival rate of larvae decreased rapidly from day 10 onwards. The larvae did not grow in the culture system. The addition of DEC did not affect the morbidity of the larvae and no difference was observed in the morphological characteristics between the larvae cultured in the presence or absence of DEC.
The infective larvae were cultured in vitro for 5 days in the presence or absence of DEC, and inoculated into jirds. The animals were necropsied at intervals, and developing larvae and adult worms were recovered. When the larvae were cultured without DEC and then inoculated subcutaneously into jirds, 29.8% of the inoculum was recovered 3–15 days, and 25% 19–22 weeks, post-inoculation. However, when the larvae were exposed to DEC in vitro and inoculated into jirds, the rate of recovery was reduced to 25% 3–15 days post-inoculation and 2% after 19–22 weeks. When the control larvae cultured in vitro were inoculated intraperitoneally into jirds, 41·3% of inoculum was recovered 3–15 days, and 42·8% 19–22 weeks, post-inoculation. Again the corresponding value for larvae exposed to DEC in vitro was reduced to 19.8% 3–15 days, and 8% 19–22 weeks, post-inoculation. It was observed that the larvae exposed to DEC in vitro were retarded in their development in jirds. These results indicate that DEC has a direct action against the infective larvae of B. pahangi .
In preceding studies by the author, use of the immunomodulator drug diethylcarbamazine resulted in the detection of antibodies to feline oncornavirus-associated cell membrane antigen in nine feline leukaemia virus infected cats that had previously given negative results to this antibody. In the present report, seven diethylcarbamazine-treated cats developed higher serum antibody titres to feline infectious peritonitis more frequently than did seven untreated controls. Since feline infectious peritonitis is caused by a coronavirus, these results suggest that diethylcarbamazine treatment could be exploited for vaccination and treatment strategies for non-retroviral in addition to retroviral infections.
The effect of diethylcarbamazine (DEC) on infective larvae and immature worms of Brugia pahangi was studied in vitro. The in vitro culture of larvae was done using the technique of Mak et al. (1983). In control cultures, most larvae remained alive for 14 days; over 50% survived until day 22 of cultivation. The addition of DEC did not affect the life span of the larvae. Among those which survived for 22 days in control cultures, 77.8% reached the fourth stage, their length being 2908.2 +/- 453.2 microns. When DEC was added to a final concentration of 0.1 mg/ml, the percentage of larvae attaining the fourth stage was reduced (42.9%) and their growth retarded; the length of the fourth-stage larvae was 2548.4 +/- 414.0 microns. The addition of 1.0 mg/ml DEC completely arrested the growth and development of the larvae.
Effects of piperazine derivatives, especially of diethylcarbamazine (DEC) on adult Angiostrongylus cantonensis and Dirofilaria immitis were examined. Piperazine (3 X 10(-5)-10(-4) M) paralyzed A. cantonensis and the action was antagonized by picrotoxin. 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP) (10(-5)-10(-4) M) caused contraction but little effect was produced by strychnine. An inhibitory effect on untreated preparations was caused by lower concentrations (3 X 10(-6)-10(-5) M) of diethylcarbamazine citrate (DEC) and also on the preparations contracted by eserine. A stimulatory effect was also seen when higher concentrations (10(-4)-3 X 10(-4) M) of this drug were applied to both preparations. The inhibitory action of DEC was antagonized by gabergic antagonists such as picrotoxin and bicuculline, but not by alpha-adrenergic antagonists like dibenamine and phentolamine. When the worm preparation was paralyzed by strychnine or hexylresorcinol (inhibitors of the release of acetylcholine in this worm), the stimulatory effect of DEC was blocked, but pyrantel (a nicotinic cholinergic agonist) contracted the paralyzed preparation. However, the effect of DEC on D. immitis (10(-7)-3 X 10(-4) M) was inhibitory, and this action was also antagonized by picrotoxin. These results suggest that the DEC inhibitory and stimulatory action is through the gabergic and cholinergic mechanisms in adult A. cantonensis and D. immitis.
The microfilaricidal effect of diethylcarbamazine was studied in the murine model of Brugia malayi microfilaremia. CFI mice with circulating microfilariae were treated with either diethylcarbamazine (6 mg kg-1 day-1) for 10 days or with normal saline. Although antibodies against crude microfilarial antigen were detected in both groups at the time of completion of therapy, the chemically induced microfilarial clearance occurred prior to the development of these antibodies. In addition, the passive transfer of antibody just prior to chemical treatment did not enhance diethylcarbamizine-induced microfilarial clearance. In vitro studies confirmed previous observations that diethylcarbamazine enhanced antibody-dependent neutrophil adherence. Microfilarial clearance was found to be due to trapping and lysis in the liver on pathologic examination. These studies demonstrate that diethylcarbamazine leads to microfilarial clearance in the liver by mechanisms that are not dependent on host antibody.
In vitro activity of diethylcarbamazine on the infective larvae, microfilariae and adult worms of Breinlia sergenti. International Journal for Parasitology. 3: 803–807. The action of diethylcarbamazine, on the infective larvae, the microfilariae and the adult worms of Breinlia sergenti, occurring in slow loris (Nycticebus coucang) is described. The drug immobilized all the three stages of the parasite. In the case of the adult worms an initial increase in the tone of the musculature followed by flaccid paralysis was observed.
The attempts to eradicate infections with Wuchereria bancrofti by means of chemotherapeutic agents have been greatly intensified during the last five years. The National Research Council listed over one hundred and twenty compounds which by 1945 had been given clinical trial in human filariasis.¹ Of all drugs used, only the antimony compounds have appeared to have beneficial effects. Of these, the pentavalent antimonial ethylstibamine has had the best antagonistic action on the filariae.² Antimony compounds apparently act on the adult filariae, the circulating embryos disappearing gradually from the blood stream. The complete disappearance of the embryos takes place from a few months, in some patients, to longer periods of time in others. A drug as yet had to be found which possessed a more marked and rapid effect on the microfilariae and the adult worms.
Hewitt³ and his co-workers have recently reported on the marked filaricidal action
The purpose of this paper is to describe the maintenance in the laboratory of a filarial infec-tion (Litomnosoides carinii) which is suitable for chemotherapeutic and other types of investigations. The strain is kept in cotton rats (Sigmodon hispi-dus) and with one interruption it has now been maintained in our department for 2 years, during which time over 600 rats have been infected as shown by the presence of microfilariae in their peripheral blood.
- R I Hewitt
- S Kushner
- H Stewart
- E White
- W S Wallace
- Y Subbarow
Hewitt, R. I., Kushner, S., Stewart, H., White, E., Wallace, W. S., and SubbaRow, Y. (1947). J.
Lab. clin. Med., 32, 1314.
- F Hawking
- P Sewell
Hawking, F., Sewell, P., and Thurston, J. (1948). Lancet, 2, 730.
- B K Harned
- R W Cunningham
- S Halliday
- R E Vessey
- N N Yuda
- M C Clark
- Y Subbarow
Harned, B. K., Cunningham, R. W., Halliday, S., Vessey, R. E., Yuda, N. N., Clark, M. C., and
SubbaRow, Y. (1948). Ann. N.Y. Acad. Sci., 50, 141.
The Rat. Data and reference tables
- H H Donaldson
Donaldson, H. H. (1924). The Rat. Data and reference tables. Philadelphia.
- D Santiago-Stevenson
- J Oliver-Gonzalez
Santiago-Stevenson, D., Oliver-Gonzalez, J., and Hewitt, R. 1. (1947). J. Amer. med. Ass., 135, 708.