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Prevalence of piroplasms in small ruminants in North-West Tunisia and the first genetic characterisation of Babesia ovis in Africa

Authors:
Mohamed Ridha Rjeibi at Institut de la recherche vétérinaire de Tunis, Tunisie
Mohamed Ridha Rjeibi
  • Institut de la recherche vétérinaire de Tunis, Tunisie
Mohamed Gharbi at Ecole Nationale de Médecine Vétérinaire de Sidi Thabet
Mohamed Gharbi
  • Ecole Nationale de Médecine Vétérinaire de Sidi Thabet
Moez Mhadhbi at Ecole Nationale de Médecine Vétérinaire
Moez Mhadhbi
Wiem Mabrouk
Wiem Mabrouk
Wiem Mabrouk
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Abstract and Figures

In this study, the prevalence of piroplasms in sheep and goats was assessed with Giemsa-stained blood smear examination, PCR and nested PCR-restriction fragment length polymorphism (RFLP) to identify Babesia and Theileria species, respectively, in 338 small ruminants (172 sheep and 166 goats) from three sites in North-West Tunisia during the 2011 summer season. The overall infection prevalence of piroplasms in Giemsa-stained blood smears was 3.2% (11/338), with a parasitaemia ranging from 0.01 to 0.05%. PCR detected two species, namely Babesia ovis (in sheep and goats) and Theileria ovis (in sheep), with an overall prevalence of 16.3%. The molecular prevalence of B. ovis was significantly higher in sheep than in goats (17.4% and 9%, respectively, p = 0.034). The same trend was observed for T. ovis in sheep and goats (5.8% and 0%, respectively, p = 0.004). Comparison of the partial sequences of the 18S ssu rRNA gene revealed 100% similarity amongst Babesia from sheep and goats. The single Theileria sequence in this study showed 100% similarity to T. ovis. A high similarity with all the blasted genotypes was reported for Theileria and Babesia sequences. This is the first molecular detection of B. ovis and genetic characterisation of small ruminants' piroplasms in Africa.
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Prevalence of piroplasms in small ruminants in North-West Tunisia and the first genetic characterisation of Babesia ovis in Afri
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Supplementary resources (3)

Babesia ovis voucher BOTNSHAD01 18S ribosomal RNA gene, partial sequence
Nucleotide Sequence
September 2013
Mohamed Ridha Rjeibi · Mohamed Gharbi · Moez Mhadhbi · I. Nasfi · Mohamed Aziz Darghouth
Babesia ovis voucher BOTNGTAD01 18S ribosomal RNA gene, partial sequence
Nucleotide Sequence
September 2013
Mohamed Ridha Rjeibi · Mohamed Gharbi · Moez Mhadhbi · I. Nasfi · Mohamed Aziz Darghouth
Theileria ovis voucher TOTNSHAD01 18S ribosomal RNA gene, partial sequence
Nucleotide Sequence
September 2013
Mohamed Ridha Rjeibi · Mohamed Gharbi · Moez Mhadhbi · I. Nasfi · Mohamed Aziz Darghouth
... Of these two, B. ovis is highly pathogenic and has been reported widely (Schnittger et al., 2003). The molecular prevalence of B. ovis has been observed to be very low or non-existent (Rjeibi et al., 2014;Hussein et al., 2017). ...
... In total, 5,631 domestic small ruminants were studied across Africa, with sheep making the bulk of these animals, with a total of 3,634 (65.53%) live heads and goats making up the rest, with 1,997 (35.46%) live heads. The eligible studies cut across every region of the continent of Africa with northern Africa comprising of eighteen studies (Salih et al., 2012;M'ghirbi et al., 2013;Taha et al., 2013;Belkahia et al., 2014;Rjeibi et al., 2014;Ben Said et al., 2015;Rjeibi et al., 2016a;Rjeibi et al., 2016b;El Imam et al., 2016;Lee et al., 2018;Aouadi et al., 2017;Hassan et al., 2019;Tumwebaze et al., 2020a;Eisawi et al., 2020;Abdullah et al., 2021;Ben Said et al., 2022;M'ghirbi et al., 2022;ElHamdi et al., 2022), followed by southern Africa with four studies (Ringo et al., 2018;Berthelsson et al., 2020;Chatanga et al., 2021;Sili et al., 2021), eastern Africa with four studies (Gebrekidan et al., 2014;Ringo et al., 2019;Tumwebaze et al., 2020b;Kasozi et al., 2021) and western Africa with four studies (Djiba et al., 2013;Dahmani et al., 2019;Onyiche et al., 2022;Adewumi et al., 2022). ...
... The majority of the studies reported the absence of infection with B. ovis in both sheep and goats (Gebrekidan et al., 2014;Lee et al., 2018;Aouadi et al., 2017;Hassan et al., 2019;Onyiche et al., 2022). So far, only three documented reports in Africa on the presence of B. ovis DNA in the blood of sheep and goats (Rjeibi et al., 2014;Tumwebaze et al., 2020b;Adewumi et al., 2022). However, the prevalence is closely associated with the distribution of the tick vector, Rhipicephalus bursa, common in the Palaearctic region, including the Mediterranean basin, with northern Africa to the south (Yeruham et al., 1998). ...
Molecular prevalence and distribution of tick-borne bacterial and protozoan pathogens of sheep and goats in Africa: A systematic review and meta-analysis
Article
Full-text available
  • Jul 2024
Tick-borne pathogens (TBPs) are a major impediment to the health, welfare, and production of small ruminants across the world, including Africa. Comprehensive information about the epidemiology of TBPs infecting sheep and goats across Africa is lacking. Therefore, this study was undertaken to determine the prevalence through a meta-analysis of selected TBPs in blood DNA from domestic sheep and goats in Africa obtained using molecular-based methods. The literature review was done according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines using five English electronic databases (PubMed, Science Direct, Springer Link, Web of Science, and African Journals Online (AJOL). The search was performed with no restriction in time through to 18 th January 2023. Of the 63 full-text articles subjected to eligibility, only 30 articles met the eligibility criteria and were included in the review. The overall pooled prevalence of selected TBPs varied considerably between host species (sheep vs. goats), with Anaplasma ovis (44.50 vs. 48.40%), Ehrlichia ruminantium (5.50 vs. 2.00%), Coxiella burnetii (4.40 vs. 1.70%), Borrelia theileri in sheep (5.20%), Babesia ovis (1.70% vs. 1.90%), Theileria ovis (40.50% vs 10.00%), T. separata (1.00% vs 1.00%) and T. lestoquardi in sheep (8.40%). However, the prevalence of the selected TBPs was generally higher in sheep compared to goats. Several genetic loci were targeted in the characterization of tick-borne pathogens, such as 16S rDNA, groEL, and msp4 for Anaplasma ovis, pCS20 for Ehrlichia ruminantium, Insertion Sequence (IS1111) for Coxiella burnetii, flaB (flagellin) and 16S rRNA for Borrelia theileri, 5.8S rRNA and 18S rRNA for Babesia/Theileria, as well as the utilization of numerous PCR variants including conventional polymerase chain reaction (PCR), nested-PCR, qPCR, Loop-mediated isothermal amplification (LAMP), and reverse line blotting (RLB). In conclusion, A. ovis was the most widely distributed and prevalent TBP affecting small ruminants within the continent. Hence, this warrants adequate attention towards early diagnosis and treatment of infected animals as well as the control of the tick vectors involved in their transmission.
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... Babesia ovis is a tick-borne disease with high morbidity and mortality in small ruminants and causes high economic losses in many tropical and subtropical regions (Shahbazi et al. 2013;Rjeibi et al. 2014). ...
... While some researchers (Iqbal et al. 2011;Esmaeilnejad et al. 2015;Gökpınar et al. 2021;Adewumi et al. 2022;Arwa and Kawan 2022) reported a higher prevalence in males, other studies (Emre et al. 2001;Rjeibi et al. 2014;Rjeibi et al. 2016;Stevanović et al. 2022) reported a higher prevalence in females. In this study, higher prevalence was found in females, but the difference was not statistically significant. ...
Molecular identification and phylogenetic analysis of Babesia ovis in sheep in Siirt, Türkiye: relationship with some oxidant/antioxidant parameters
Article
Full-text available
  • Dec 2024
  • ACTA VET BRNO
The Babesia genus includes tick-borne haemoprotozoan parasites that infect a wide variety of vertebrate hosts, both domestic and wild, around the world. Babesia spp. cause oxidative stress by increasing the number of free radicals in erythrocytes. Among this genus, Babesia ovis causes babesiosis in sheep and goats, especially in tropical and subtropical regions, causing significant economic losses. In this study, we aimed to determine the presence and prevalence of B. ovis in sheep in Siirt province, Türkiye, using molecular method and to evaluate some oxidant/antioxidant parameters in infected sheep. The animal material used in this study consisted of a total of 500 sheep. DNA extraction, Polymerase Chain Reaction (PCR) amplification and sequence analysis of blood samples and Enzyme-Linked ImmunoSorbent Assay (ELISA) analysis of serum samples were performed. As a result of the study, 84 of the 500 samples (16.80%) examined were PCR positive. Advanced oxidation protein products (AOPP) and nitric oxide (NO) concentrations were found to be higher in sheep with babesiosis compared to the control group. Superoxide dismutase (SOD) activity was higher in the control group and catalase (CAT) activity was higher in infected sheep. As a result of this study, the presence of Babesia ovis was detected in all districts of Siirt province. It has been determined that infection caused by Babesia ovis in sheep causes oxidative stress as a result of increased nitric oxide and oxidized protein levels and this process may participate in the pathology of the disease.
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... In goats, no difference in the seroprevalence of Theileria infection was reported between females and males (Luo et al., 2017). In sheep, the molecular prevalence of T. ovis did not vary significantly for age categories, while females were significantly more infected than males (Rjeibi et al., 2014). The effect of associated host factors on the susceptibility to infection is not fully well understood. ...
... Different species belonging to Hyalomma, Haemaphysalis and Rhipicephalus, which are distributed in Africa's tropical and subtropical regions, could transmit Theileria spp. in small ruminants (Stuen, 2020). The presence of T. ovis in sheep and goats has been confirmed in North African countries such as Algeria and Tunisia using molecular approaches (Sadeddine et al., 2020;Aouadi et al., 2017;Rjeibi et al., 2014;M'ghirbi et al., 2013). T. ovis was a non-pathogenic species for infected animals (Aouadi et al., 2017;M'ghirbi et al., 2013). ...
Seroprevalence of Theileria ovis in Goats from M’Sila Region, Central Algeria
Article
Full-text available
  • Oct 2024
Background: In Algeria, data on the epidemiology of theileriosis in small ruminants are limited. Objectives: The current study investigates the seroprevalence of Theileria spp. in goats from the M’Sila region, Central Algeria. Methods: Blood samples of 128 goats from 19 farms were collected from the locality of Maâdid. The indirect fluorescence antibody test (IFAT) was performed to test the goats’ sera for antibodies against Theileria ovis and Theileria lestoquardi. Results: Out of 128 tested samples, 21 sera (16.40%) were positive for T. ovis antibodies. All samples were seronegative for T. lestoquardi. The seroprevalence of T. ovis varied from 10% to 30% on farms. The seropositivity rates did not differ significantly with age, sex, or breeding system of goats. Tick-infested goats were significantly more seropositive than no-infested goats. Conclusion: The present study reports essential data on the epidemiology of caprine theileriosis from Central Algeria.
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... In Iran, Iraq, Egypt, Israel, Spain, India and Pakistan, in addition to the Babesia species, the Anaplasma ovis parasite belonging to the Anaplasma genus of the Anaplasmatacea family of the Rickettsiales order, is also noted the intensively spreading in small ruminants. The researchers have researched the blood samples of sheep and goats by classical and ELISA methods according to the Babesia and Anaplasma parasites and determined that the infection was high 21,22,23,24,25,26,27 (Esmaeilnejad, 2014;Renneker, 2013;Rjeibi, 2014;Yeruham, 1995;Ferrer, 1998;Baby, 2001;Adil and Arif, 2022). Researches were conducted in the spring, summer and autumn seasons of 2022 in livestock farms of Neftchala, Bilasuvar, Salyan, Hajigabul, Shirvan districts of Shirvan-Salyan economic region. ...
... In Iran, Iraq, Egypt, Israel, Spain, India and Pakistan, in addition to the Babesia species, the Anaplasma ovis parasite belonging to the Anaplasma genus of the Anaplasmatacea family of the Rickettsiales order, is also noted the intensively spreading in small ruminants. The researchers have researched the blood samples of sheep and goats by classical and ELISA methods according to the Babesia and Anaplasma parasites and determined that the infection was high 21,22,23,24,25,26,27 (Esmaeilnejad, 2014;Renneker, 2013;Rjeibi, 2014;Yeruham, 1995;Ferrer, 1998;Baby, 2001;Adil and Arif, 2022). Researches were conducted in the spring, summer and autumn seasons of 2022 in livestock farms of Neftchala, Bilasuvar, Salyan, Hajigabul, Shirvan districts of Shirvan-Salyan economic region. ...
The Taxonomıc Research of the Prımıtıve Blood Parasıtes and Transmıttıng Ixodıdae Tıcks of the Small Ruminants in the Shırvan-Salyan Economıc Regıon of Azerbaıjan
Article
Full-text available
  • Mar 2024
  • Biosci., Biotechnol. Res. Asia
The primitive blood parasites - piroplasmids are pathogens transmitted to the agricultural animals by the ticks and caused the death and serious economic damage. In Azerbaijan, in the economic regions where the animal husbandry is developed, the systematic investigation and epizootology of these parasites in small ruminants, were researched by us for the first time. For this purpose, the research work was conducted in the Shirvan-Salyan economic region. For this purpose, researches were conducted on the taxonomic study of primitive blood parasites and their transmitters - Ixodidae ticks of small ruminants in the Shirvan-Salyan economic region. Out of 887 sick and suspected diseases sheep, 483 heads (54.5%), and 125 heads (27.4%) of 456 goats had positive results of peripheral blood smear samples attributed to primitive blood parasites. Babesia ovis and Anaplasma ovis parasites were detected in the erythrocytes of sick sheep, and the infection was mostly associated. A.ovis parasite was detected in sero samples of goats. The organs of 56 sheep and 31 goats that died of high fever - spleen, kidney, liver - were examined for primitive blood parasites. The results of the classical examination method in the diagnosis of A.ovis and B.ovis parasites were compared with the effectiveness of the polymerase chain reaction (PCR). 2,875 sheep and goats (1,786 sheep, 1,089 goats) were examined for ectoparasites in livestock farms, 63.8 percent of sheep and 53.6 percent of goats were intensively infected with ticks. Tick infestation was mostly covered in spring, summer and autumn with high intensity. Rhipicephalus bursa ticks were dominant in sheep and Hyalomma plumbeum ticks in goats. In order to determine transovarial and transstadial transmission of disease agents, smears made from internal organs (salivary gland, ovary, intestine) and eggs of ticks were studied for A.ovis and B.ovis parasites.
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... Of these, B. ovis is one of the first identified Babesia spp. caused by clinical infection with high mortality in tropical and subtropical countries [8][9][10]. ...
Experimental infection of purebred Saanen goats high pathogenicity and virulence of Babesia aktasi
Article
Full-text available
Small ruminant babesiosis remains a neglected disease despite causing significant economic losses to sheep and goat herds in many regions around the world. The pathogenesis and clinical manifestations of ovine babesiosis are well-known, but there is a lack of information regarding caprine babesiosis. Since the discovery of the first Babesia spp. in 1888, several species/subspecies/genotypes, including Babesia aktasi, have been described. Our recent molecular survey revealed that the parasite is highly prevalent (22.5%) in indigenous goats from Mediterranean region of Türkiye. The aim of this experimental study was to determine the pathogenicity and virulence of B. aktasi in immunosuppressed (n = 5) and immunocompetent (n = 7) purebred Saanen goats. The goats were experimentally infected with fresh B. aktasi infected blood, and examined for clinical, parasitological, hematological, and serum biochemical findings throughout the infection. Following the parasite inoculation, intra-erythrocytic parasites were detected from the 1st day post-infection, followed by an increase in rectal temperature and parasitemia. The parasitemia was detected ranging from 4.3% to 33.5% in the immunosuppressed group, while it was 2.1% to 7.6% in the immunocompetent. Severe clinical symptoms characterized by anemia, jaundice, and hemoglobinuria developed in both groups. A statistically significant inverse correlation was observed between the increase in parasitemia and RBC, WBC, HCT, and Hb values in the goats compared to pre-infection levels. Values of AST, ALT, GGT, Total bilirubin, and Albumin showed a significant increase, with all the immunosuppressed goats dying on the 4th and 7th days post-infection, while four out of seven immunocompetent goats died on between 6-8th days. Severe edema in the lungs, frothy fluid in the trachea, jaundice in the subcutaneous and mesenteric fat, and dark red urine were detected in necropsy. The results obtained in this study demonstrated that B. aktasi was highly pathogenic to purebred Saanen goats. Current work assures valuable insights into the pathogenesis and virulence of B. aktasi and serves as a foundation for future studies to develop effective control strategies against caprine babesiosis.
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... Important hemoparasitic diseases of livestock with special reference to small ruminants are; theileriosis, anaplasmosis, and babesiosis (Razzaq et al., 2015). Theileriosis in small ruminants is caused by different species but Theileria lestoquardi, causing malignant ovine theileriosis, is extremely pathogenic (Hakimi et al., 2019) and is equivalent to T. annulata infection in cattle whereas T. ovis is slightly pathogenic in small ruminants (Rjeibi et al., 2014) and all other species (T. separate, T. uilenbergi, T. recondite) are almost avirulent (Aydin et al., 2013). ...
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... Barbarine animals were significantly more infested by ectoparasites (16.8%) than QFO animals (0.8%) (p < 0.0001). This result is in contrast with those reported by Rjeibi et al. [61], who did not find any difference in infestation prevalence by ticks between Barbarine and Queue Fine de l'Ouest breeds in Northwest Tunisia (humid region). Indeed, in Siliana district (Northwest of Tunisia), Barbarine sheep were significantly less infested by ticks (7.3%) compared to cross-bred (19.1%) and QFO (16.7%) sheep. ...
Repeated Cross-Sectional Survey of Ectoparasites in Sheep from Central Tunisia: Does Low Prevalence Indicate Good Hygiene or Resistance to Ectoparasites?
Article
Full-text available
  • Mar 2024
Simple Summary Sheep ectoparasites such as chewing lice, fleas and ticks are serious impediments to sheep productivity. They cause enormous losses of wool and leather due to the skin lesions they cause, which reduces the market value of sheep. Some of these ectoparasites are also vectors of several pathogens. In the present study, we aim to investigate the ectoparasite population infesting 1243 autochthonous sheep in Tunisia from two breeds, Barbarine and Queue Fine de l’Ouest. A total of 74 sheep (5.95%) were infested by 3 groups of ectoparasites. The low prevalence of ectoparasite infestation in sheep reported here may be due to possible genetic resistance or simply to successful hygiene and management measures implemented by farmers. Abstract Sheep ectoparasites such as chewing lice, fleas and ticks are serious constraints to sheep productivity and are the cause of skin lesions in animals that decrease their market value. This study aims at investigating the ectoparasite fauna infesting small ruminants in the district of Sidi Bouzid (central Tunisia). A total of 1243 Barbarine and Queue Fine de l’Ouest (QFO) sheep were examined every two months for one year. Of the total animals examined, 74 were infested by at least 1 parasite group (5.95%). Three ectoparasite groups were identified as Psoroptes ovis (0.48%; 6/1243), ticks (5.3%; n = 66/1243) and one specimen of Ctenocephalides canis (0.08%; n = 1/1243). The most abundant tick among the 358 specimens was Rhipicephalus sanguineus sensu lato (n = 337; 94.1%), followed by Hyalomma impeltatum (n = 7/358; 1.9%), H. dromedarii (n = 7/358; 1.9%), H. excavatum (n = 5/358; 1.4%) and only two specimens of H. scupense (n = 2/358; 0.55%). The sheep herds showed low infestation prevalence by ectoparasite over the year, with a significant difference according to the seasons (p < 0.05). A higher infestation prevalence was recorded in March (14.36%). Barbarine sheep breed showed significantly higher infestation prevalence (16.8%) compared to QFO (0.8%) (p < 0.01). There were no differences in infestation prevalence according to sex of the animal or age groups. Knowledge of the ectoparasite population harboured by sheep, its activity dynamics and risk factors is required to develop effective ectoparasite control options. The low prevalence of ectoparasite infestation in sheep reported here may be due to possible genetic resistance or simply to successful hygiene measures implemented by farmers.
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Assessment of Babesia ovis pathogenicity in goats: implications for transmission dynamics and host resistant
Article
Full-text available
  • Nov 2024
Babesia ovis, commonly associated with ovine babesiosis, poses a significant threat to sheep health, often resulting in severe clinical manifestations and high mortality rates. However, the impact of B. ovis on goats has remained uncertain, prompting us to investigate its pathogenicity in caprine hosts. Experimental infections using B. ovis-infected blood inoculation and infected tick infestation, were conducted on spleen-intact (n=5) and splenectomized (n=5) goats. The experimental infection was performed using fresh blood obtained from a B. ovis-infected splenectomized sheep. One spleen-intact sheep served as a control for the experimental infection with B. ovis-infected Rhipicephalus bursa ticks. While all experimentally infected sheep (#501, #575) displayed severe clinical symptoms and high parasitemia, goats exhibited resistance, showing no significant clinical manifestations or sustained parasitemia. Notably, B. ovis was detected in two spleen-intact goats via nested PCR, prompting further investigation into their role as reservoirs for tick-borne transmission. These goats were then infested with Babesia spp.-free R. bursa larvae (0.1 gr) and adults (50 females and 50 males) for transstadial and transovarial transmission experiments respectively. Results indicated that chronically B. ovis-infected spleen-intact goats are not significant sources for maintaining the tick-borne transmission cycle of the parasite. These findings highlight the differential susceptibility of goats to B. ovis infection compared to sheep and their limited role as reservoirs for parasite transmission. Understanding the role of goats in B. ovis transmission and their resistance mechanisms can inform effective control measures and reduce economic losses in affected regions. Further research into caprine babesiosis and host immunological responses is essential to fully elucidate their possible role as reservoirs of the parasite, and underlying mechanisms of host susceptibility and parasite pathogenesis.
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veterinerdogumjinekolojiozel8-1-20 Küçük Ruminantlarda Kan Protozoonları, Epidemiyoloji, İzleme ve Eradikasyon Stratejileri Blood Protozoa in Small Ruminants, Epidemiology, Monitoring and Eradication Strategies
Chapter
Full-text available
  • Jan 2024
K üçükbaş hayvan yetiştiriciliği, yoksul kırsal toplumlarda ve az gelişmiş ülke-lerde et, süt, yapağı ve deri üretimi alanlarındaki ihtiyaçların karşılanmasında önemli bir geçim kaynağı oluşturmaktadır. 1 Ülkemizde de dünyada olduğu gibi yaygın olarak yapılan koyun ve keçi yetiştiriciliği, tarımsal ekonominin önemli bir parçasını oluşturmaktadır. Türkiye İstatistik Kurumu (TÜİK) 2020 verilerine göre Türkiye'de 42.126.781 baş koyun ve 11.985.845 baş keçi bulunmaktadır. Sağımı ya-pılan koyunlardan yıllık 1.521.456 ton, keçilerden 577.209 ton süt elde edilmektedir. Yine TUİK 2019 verilerine göre ülkemizde 109.382 ton koyun, 16.536 ton keçi eti üre-tilmiştir. Tarımsal ekonomide büyük paya sahip olan küçükbaş hayvan işletmelerinde verim kaybı oluşturabilecek her türlü hastalık etkeni önem arz etmektedir. GENEL BİLGİLER BaBesia Ixodid keneler ile biyolojik olarak nakledilen Babesia türleri intraeritrositik yerleşim gösteren ve memeli hayvanlarda Trypanosoma'lardan sonra en yaygın görülen kan pro-125 ÖZET Koyun keçi yetiştiriciliği; et, süt, yapağı ve deri üretimi alanlarında insanların ihtiyaçlarının karşılanmasında ve tarımsal ekonomide önemli bir kaynak oluşturmaktadır. Bu nedenle hayvanlarda verim kaybına neden olabilecek her türlü hastalık etkeni önem arz etmektedir. Koyun ve keçilerde ciddi verim kayıplarına sebep olan Babesia/Theileria türleri tropik ve subtropik bölgelerde yaygınlık gös-termektedir. Özellikle ilkbahar ve yaz aylarında vektör kene aktivasyonuna bağlı olarak hastalık oranı artmaktadır. Babesia/Theileria türleri mikroskobik, serolojik ve moleküler teşhis yöntemleriyle tespit edilebilmektedir. Tedavi edilmeyen ya da tedaviye geç kalınan vakalarda mortalite yüksek seyretmek-tedir. Hastalığı tedavi etmekten ziyade koruyucu önlemlerin alınması daha çok önem taşır. Aşı uygu-laması bu konudaki en etkili yöntem olmakla birlikte koyun ve keçilerde Babesia/Theileria türlerine yönelik ticari bir aşı mevcut değildir. Vektör kenelere yönelik çalışmalarda çeşitli kontrol mekaniz-maları geliştirilmiş ve yapılan çalışmalarda başarılı sonuçlar elde edilmiştir. Anah tar Ke li me ler: Babesia/Theileria; küçük gevişgetiren ABS TRACT Small ruminant breeding is an important resource in meeting the needs of people in the fields of meat, milk, wool, and leather production, and the agricultural economy. Therefore, all the disease agents that may cause productivity loss in animals become important. Babesia/Theileria species which cause serious productivity losses in sheep and goats are prevalent in tropical and subtropical regions. The diseases have a high prevalence especially in the spring and summer months due to vector tick activation. Babesia/Theileria species can be detected by microscopic, serological, and molecular diagnostic methods. Mortality can be high in untreated or in delayed cases. It is more important to take preventive measures than to treat the disease. Vaccination is the most effective method in this regard. However, a vaccine for Babesia/Theileria species in sheep and goats has not been developed. Various control mechanisms have been developed in studies on vector ticks and successful results have been achieved.
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CONFIDENCE LIMITS ON PHYLOGENIES: AN APPROACH USING THE BOOTSTRAP
Article
  • Jul 1985
  • EVOLUTION
The recently-developed statistical method known as the "bootstrap" can be used to place confidence intervals on phylogenies. It involves resampling points from one's own data, with replacement, to create a series of bootstrap samples of the same size as the original data. Each of these is analyzed, and the variation among the resulting estimates taken to indicate the size of the error involved in making estimates from the original data. In the case of phylogenies, it is argued that the proper method of resampling is to keep all of the original species while sampling characters with replacement, under the assumption that the characters have been independently drawn by the systematist and have evolved independently. Majority-rule consensus trees can be used to construct a phylogeny showing all of the inferred monophyletic groups that occurred in a majority of the bootstrap samples. If a group shows up 95% of the time or more, the evidence for it is taken to be statistically significant. Existing computer programs can be used to analyze different bootstrap samples by using weights on the characters, the weight of a character being how many times it was drawn in bootstrap sampling. When all characters are perfectly compatible, as envisioned by Hennig, bootstrap sampling becomes unnecessary; the bootstrap method would show significant evidence for a group if it is defined by three or more characters.
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The Neighbor-Joining Method: A New Method for Reconstructing Phylogenetic Trees
Article
  • Jul 1987
  • MOL BIOL EVOL
A new method called the neighbor-joining method is proposed for reconstructing phylogenetic trees from evolutionary distance data. The principle of this method is to find pairs of operational taxonomic units (OTUs [= neighbors]) that minimize the total branch length at each stage of clustering of OTUs starting with a starlike tree. The branch lengths as well as the topology of a parsimonious tree can quickly be obtained by using this method. Using computer simulation, we studied the efficiency of this method in obtaining the correct unrooted tree in comparison with that of five other tree-making methods: the unweighted pair group method of analysis, Farris's method, Sattath and Tversky's method, Li's method, and Tateno et al.'s modified Farris method. The new, neighbor-joining method and Sattath and Tversky's method are shown to be generally better than the other methods.
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