Alfons Renz

Alfons Renz
University of Tuebingen | EKU Tübingen · Institute of Evolution and Ecology

Privatdozent, Dr. rer. nat.

About

105
Publications
10,621
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2,013
Citations
Citations since 2016
29 Research Items
613 Citations
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2016201720182019202020212022020406080100120
2016201720182019202020212022020406080100120
2016201720182019202020212022020406080100120
Introduction
For the ongoing research project in Cameroon, see: www.riverblindness.eu For teaching activities at the university of Tübingen see: www.vektorbiologie.uni-tuebingen.de For our book "Wenk & Renz, Biologie der Humanparasiten" see: www.parasitologie-wenk-renz.de
Additional affiliations
January 2002 - present
University of Tuebingen
Position
  • Privatdozent
January 1996 - December 2001
University of Hohenheim
January 1992 - December 2002
University of Liverpool
Description
  • Macrofil - Search for new drugs against Onchocerca filarial worms
Education
September 1969
University of Tuebingen
Field of study
  • Biology, Zoology, Parasitology

Publications

Publications (105)
Article
Full-text available
The genus Haemaphysalis Koch, 1844 (Acari: Ixodidae) is the second-largest genus, with more than 170 described species that primarily parasitize mammals and birds (Guglielmone et al. 2014, Guglielmone et al. Zootaxa 4871(1): 001-322, 2020). Haemaphysalis species are three-host ticks, mainly distributed in southern and southeastern Asia and tropical...
Article
Purpose: The occurrence of Single-Nucleotide Polymorphisms (SNPs) associated with repeated ivermectin treatment and sub-optimal responses reported by previous findings is of great concern in Onchocerciasis endemic areas. This study investigated SNPs' occurrence after 15 years of ivermectin intervention in Onchocerciasis endemic communities in two...
Article
Full-text available
Autochthonous taurine and later introduced zebu cattle from Cameroon differ considerably in their resistance to endemic pathogens with little to no reports of the underlying genetic make-up. Breed history and habitat variations are reported to contribute significantly to this diversity worldwide, presumably in Cameroon as well, where locations dive...
Preprint
Full-text available
Background: A better understanding of parasite population genetic processes in specific biogeography is needed to support onchocerciasis elimination goals. The genetic diversity of Onchocerca microfilariae was explored by amplifying a fragment of the 16S rRNA gene in the endemic area in Taraba State, Nigeria, Methods: Eight (8) communities were se...
Article
Full-text available
Background During the last two decades research on animal filarial parasites, especially Onchocerca ochengi, infecting cattle in savanna areas of Africa revealed that O. ochengi as an animal model has biological features that are similar to those of O. volvulus, the aetiological agent of human onchocerciasis. There is, however, a paucity of biochem...
Article
Full-text available
Background: African indigenous taurine cattle display unique adaptive traits shaped by husbandry management, regional climate and exposure to endemic pathogens. They are less productive with respect to milk and meat production which has been associated with amongst others, small size, traditional beliefs, husbandry practices, limited feed resource...
Poster
Full-text available
Intense cattle farming in the Ngaoundere highland savannah diverted Simulium vectors to the non-human blood-hosts and Onchocerca ochengi induce some degree of cross-reacting premunition and zooprophylaxis. Savannah areas are also endemic for many tropical infectious agents. The associations of these parasites can be mutualistic as well as antagon...
Article
Gastro-intestinal tracts were examined from thirteen Gudali zebu cattle, ten goats and ten sheep from the Adamawa highland in Northern Cameroon. A total of 28,325 adult helminths were recovered from the abomasa, small and large intestines. Five trichostrongylid genera were identified by their morphology: Haemonchus, Trichostrongylus and Oesophagost...
Preprint
Full-text available
Background West African indigenous taurine cattle display unique adaptive traits shaped by husbandry management, regional climate and exposure to endemic pathogens. They are less productive with respect to milk and meat production which has been associated with a number of factors, amongst others small size, traditional beliefs and husbandry practi...
Preprint
Full-text available
Background: West African indigenous taurine cattle display unique adaptive traits shaped by husbandry management, regional climate and exposure to endemic pathogens. They are less productive with respect to milk and meat production which has been associated with amongst others, small size, traditional beliefs and husbandry practices. This resulted...
Preprint
Full-text available
Background: West African indigenous taurine cattle display unique adaptive traits shaped by husbandry management, regional climate and exposure to endemic pathogens. They are less productive with respect to milk and meat production which has been associated with amongst others, small size, traditional beliefs and husbandry practices. This resulted...
Article
Full-text available
Background: African animal trypanosomosis remains the major constraint of livestock production and livelihood of pastoral communities in Cameroon. Despite several decades of vector and parasite control efforts, it has not been eradicated. Alternative and sustainable control strategies require a sound knowledge of the local species, strains and vec...
Article
Full-text available
Background: Public interest for tick-borne pathogens in cattle livestock is rising due to their veterinary and zoonotic importance. Consequently, correct identification of these potential pathogens is crucial to estimate the level of exposition, the risk and the detrimental impact on livestock and the human population. Results: Conventional PCR...
Article
Full-text available
A cattle exposure trial was carried out in an experimental cattle farm located in Galim near Ngaoundere. Observations were made from October–November 2016 and January 2017. Exposure commenced in the morning (8 h) and ended in the night (20h). The observed number of the different boophilic insect-groups was: Stomoxys (17,453), culicids (8925), Simul...
Article
Full-text available
In Africa, pathogens transmitted by ticks are of major concern in livestock production and human health. Despite noticeable improvements particularly of molecular screening methods, their widespread availability and the detection of multiple infections remain challenging. Hence, we developed a universally accessible and robust tool for the detectio...
Conference Paper
Full-text available
OBJECTIVES:  Identify and determine the abundance of Stomoxys spp.  Screen legs and mouth parts of S. niger niger for FMDV.
Article
Full-text available
Background The front line molecules from filarial worms and other nematodes or helminthes are their Excretory-Secretory (ES) products. Their interaction with the host cells, proteins and immune system accounts for the skin and eye pathology or hyposensitivity observed in human onchocerciasis. ES products and adult worms’ crude extracts from Onchoce...
Article
Full-text available
Onchocerca ochengi is a nodule-forming filarial nematode parasite of cattle. It is the closest known relative of the human parasite Onchocerca volvulus, with which it shares the black fly vector Simulium damnosum. Onchocerca sp. “Siisa” was described in black flies and in cattle and, based on limited mitochondrial sequence information, appeared to...
Conference Paper
Full-text available
Introduction There is a need for replacing the human fly-collector by an automatic trap for monitoring the success of ongoing onchocerciasis control. Objectives The Simulium-trap should be specific, i.e. attract and catch only blood-hungry female flies record the time of landing, measure and automatically store environmental parameters, and finall...
Article
Full-text available
Background Genetic surveillance of the human filarial parasite, Onchocerca volvulus, from onchocerciasis endemic regions will ideally focus on genotyping individual infective larval stages collected from their intermediate host, Simuliid blackflies. However, blackflies also transmit other Onchocerca species, including the cattle parasite O. ochengi...
Preprint
Full-text available
Background Genetic surveillance of the human filarial parasite, Onchocerca volvulus , from onchocerciasis endemic regions will ideally focus on genotyping individual infective larval stages collected from their intermediate host, Simuliid blackflies. However, blackflies also transmit other Onchocerca species, including the cattle parasite O. ocheng...
Conference Paper
Full-text available
Transmission of the human filarial nematode Onchocerca volvulus is typically monitored using molecular pool screening techniques and dissection of the Simulid blackly vector. Black flies from disease endemic regions also co-transmit a range of other Onchocerca spp, which can be difficult to distinguish form the human parasite based on morphological...
Article
Full-text available
Background: Recent reports of transmission interruption of Onchocerca volvulus, the causing agent of river blindness, in former endemic foci in the Americas, and more recently in West and East Africa, raise the question whether elimination of this debilitating disease is underway after long-term treatment of the population at risk with ivermectin....
Data
Infection rate of female nulliparous flies and aquatic larvae of Simulium damnosum s.l. at two different sites in Northern Cameroon. Those infection percentages from mermithids, fungus and malpighian nematodes are given from nulliparous female flies and aquatic Simulium larvae, respectively, and those from planidium larvae from all flies dissected....
Article
Full-text available
Onchocerca ochengi is a nodule-forming filarial nematode parasite of cattle in tropical Africa and closely related to the human pathogen Onchocerca volvulus. The adult worms reside in intradermal nodules. While females are sedentary, males may move between nodules. The first stage larvae (microfilariae) disperse in the skin of the host waiting to b...
Article
Full-text available
Onchocerca volvulus is a tissue-dwelling, vector-borne nematode parasite of humans and is the causative agent of onchocerciasis or river blindness. Natural infections of BALB/c mice with Litomosoides sigmodontis and of cattle with Onchocerca ochengi were used as models to study the immune responses to O. volvulus-derived recombinant proteins (OvALT...
Article
Full-text available
In hochendemischen Gebieten können schon die jüngsten Altersklassen der menschlichen Bevölkerung zu über 90% von Plasmodium, den Erregern der Malaria, befallen sein. Trotz erheblicher Sterblichkeit, vor allem der Kinder, wird die Existenz dieser Bevölkerungen ungeachtet schlechter Ernährung und anderer, z.B. viraler und bakterieller Infektionen auc...
Article
Onchocerca ochengi, a filarial nematode parasite from African Zebu cattle is considered to be the closest relative of O. volvulus, the causative agent of river blindness. Both Onchocerca species share the vector, black flies of the Simulium damnosum complex. Correct identification of their infective third-stage larvae in man-biting vectors is cruci...
Data
Skin-microfilaria of Onchocerca ochengi moving through a thick medium. Note, that this movement is fast and directed. Thus the microfilaria advances about 1 mm in a few seconds. This directed movement shall help her to reach the site where a Simulium vector fly bites. During her life (several months or years), a microfilaria could quickly migrate t...
Article
Full-text available
Onchocerca ochengi is a filarial nematode parasite of African cattle and most closely related to Onchocerca volvulus, the causing agent of river blindness. O. ochengi females induce the formation of a nodule in the dermis of the host, in which they remain sedentary in very close association with the host's tissue. Males, which do not adhere to the...
Article
Full-text available
Parasitism refers to a particular symbiosis (deBary 1879) of organisms that live at the cost of their hosts. Virulent microbes (viruses and bacteria) proliferate unlimited causing toxic infections that end either by the host's death or its protective immunity. By this opposing survival strategy, via the population density, i.e. the contact rate, fi...
Article
Full-text available
Onchocerca volvulus, the causative agent of river blindness, is transmitted through the black fly Simulium damnosum s.l., which breeds in turbulent river waters. To date, the number of flies attacking humans has only been determined by standard fly collectors near the river or the village. In our study, we counted the actual number of attacking and...
Data
Children of Bolo. Pictures from Bolo and Galim: the village, villagers and the breeding sites are shown.
Data
The village of Bolo, main road. Pictures from Bolo and Galim: the village, villagers and the breeding sites are shown.
Data
Breeding site at the river Dilolo. Pictures from Bolo and Galim: the village, villagers and the breeding sites are shown.
Data
Children working at the river Dilolo. Pictures from Bolo and Galim: the village, villagers and the breeding sites are shown.
Data
Breeding site at the Vina du Sud. Pictures from Bolo and Galim: the village, villagers and the breeding sites are shown.
Data
"Test-person" OS with his family in front of their home. Pictures from Bolo and Galim: the village, villagers and the breeding sites are shown.
Data
"Test-person" CK in his working gear. Pictures from Bolo and Galim: the village, villagers and the breeding sites are shown.
Data
The village of Galim, main road. Pictures from Bolo and Galim: the village, villagers and the breeding sites are shown.
Article
Garments, impregnated with Diethyl-toluamid (“Deet”), were tested in areas where onchocerciasis is hyperendemic against the vector flies, namely Simulium squamosum in the rain-forest and S. damnosum s. str./S. sirbanum in the Sudan savanna. The wearing of garments (long trousers and jacket with hood, made of wide-mesh material), impregnated with 12...
Article
Full-text available
The population biology of internal parasites is difficult to study because the adult parasites are often inaccessible, deep within the host's body. Developing stages, such as eggs in the faeces or larvae in the skin are more easily obtained, but are difficult to handle because they are often very small and with a tough cuticle. This has limited the...
Article
Full-text available
Human onchocerciasis or river blindness, caused by the filarial nematode Onchocerca volvulus, is currently controlled using the microfilaricidal drug, ivermectin. However, ivermectin does not kill adult O. volvulus, and in areas with less than 65% ivermectin coverage of the population, there is no effect on transmission. Therefore, there is still a...
Article
Full-text available
Epidemiological evidence has led to the hypothesis that the concurrent and predominant transmission of Onchocerca ochengi by Simulium damnosum s.l. in sub-Saharan Africa could lead to the protection of humans against onchocerciasis caused by Onchocerca volvulus (zooprophylaxis). To gain support for this hypothesis, we investigated whether exposure...
Article
The proportion of vector blood meals taken on humans (the human blood index, h) appears as a squared term in classical expressions of the basic reproduction ratio (R(0)) for vector-borne infections. Consequently, R(0) varies non-linearly with h. Estimates of h, however, constitute mere snapshots of a parameter that is predicted, from evolutionary t...
Article
Full-text available
Here we analyze patterns of human infection with Onchocerca volvulus (the cause of river blindness) in different continents and ecologies. In contrast with some geohelminths and schistosome parasites whose worm burdens typically exhibit a humped pattern with host age, patterns of O. volvulus infection vary markedly with locality. To test the hypoth...
Article
Full-text available
Directional gyros and artificial horizons with their rotors suspended in two gimbals are well-known instruments in navigation. It is widely accepted that the first device showing already this kind of rotor support is an apparatus developed about 200 years ago at the University of Tübingen by Prof. Friedrich Bohnenberger. The original version of thi...
Article
Full-text available
Development of a drug lethal to adult Onchocerca volvulus (i.e., macrofilaricide) is a research priority for the control of human onchocerciasis. Using bovine O. ochengi infections, we investigated the effects of oxytetracycline administered in a short intensive regimen (SIR; 10 mg/kg daily for 14 days), compared with a prolonged intermittent regim...
Article
Full-text available
Ivermectin (Mectizan, Merck and CO. Inc.) is being widely used in the control of human onchocerciasis (Onchoverca volvulus) because of its potent effect on microfilariae. Human studies have suggested that, at the standard dose of 150 microg/kg an annual treatment schedule of ivermectin reversibly interferes with female worm fertility but is not mac...
Article
Full-text available
Ngaoundere Gudali zebu cattle naturally exposed to Simulium damnosum s.l. and Culicoides spp. bites were examined during 4 years for O. ochengi adult worm acquisition, Onchocerca ochengi and Onchocerca gutturosa skin microfilaria dynamics, and IgG1 and IgG2 antibody subclass responses. Eleven animals acquired a total of 465 O. ochengi nodules (aver...
Article
Full-text available
Background The Onchocerciasis Control Program (OCP) in West Africa has been closed down at the end of 2002. All subsequent control will be transferred to the participating countries and will almost entirely be based on periodic mass treatment with ivermectin. This makes the question whether elimination of infection or eradication of onchocerciasis...
Article
Full-text available
We studied the effect of 10 annual distributions of ivermectin for control of human onchocerciasis on the reduction of Onchocerca volvulus transmission by Simulium vector flies. Prevalence and infection load in the human population decreased, whilst the annual biting rates (ABR) of the vector remained unchanged. The annual transmission potential of...
Article
Full-text available
The intensity of natural transmission of Onchocerca ochengi and Onchocerco volvulus by anthropo-boophilic Simulium damnosum s.l. was studied longitudinally in two cattle watering sites of a cattle ranch within a predominantly cattle populated area of the Guinea savanna of Cameroon and related to cattle O. ochengi skin microfilaria abundance. During...