Some factors affecting the prevalence of Trypanosoma evansi in camels in Mauritania

Biting Flies and Associated Pathogens in Camels in Amibara District of Afar Region, Ethiopia

Biting flies and associated pathogens are the major health constraints on camel production and productivity and are implicated in causing significant economic losses in the pastoralist community in Ethiopia. A cross-sectional study was conducted to estimate the prevalence of biting flies and their associated pathogens in relation to different risk factors in camels in the Amibara district, from October 2019 to April 2020. A total of 480 camels were examined for biting flies and associated pathogens. The study revealed that overall, 87% (418/480) and 18% (87/480) of camels were infested by one or more biting flies and infected with Trypanosoma evansi during the study period, respectively. The collected biting flies were identified into a total of 3 genera: Hippobosca, Stomoxys, and Tabanus under the stereomicroscope. In the present study, Hippobosca (40.4%) was the most prevalent biting fly, followed by Stomoxys (31%) and Tabanus (28.6%), which affected camels in the study area. Among camels infected with Trypanosoma evansi, 7.3% and 16% were positive for parasitological and serological tests, respectively. Age, body condition score, and season appeared to have a significant effect (p ≤ 0.005) on the prevalence of biting flies and T. evansi on dromedaries. According to the findings of this study, biting flies and Trypanosoma evansi were the most common limitations on camel health, production, and productivity in the study area. As a result of the possible threat of biting flies' infestation and Trypanosoma evansi on camels, all-around attention is required in terms of strategic acaricide application, proper antiprotozoal drug use, and raising knowledge about acaricide use to prevent and control biting flies' infestation.

Recent Progress in the Detection of Surra, a Neglected Disease Caused by Trypanosoma evansi with a One Health Impact in Large Parts of the Tropic and Sub-Tropic World

Surra is a wasting disease triggered by infection with Trypanosoma evansi, a protozoan blood parasite that causes mortality and morbidity in a broad spectrum of wild and domestic animals and occasionally humans. Trypanosoma evansi has the widest geographical spread among all pathogenic trypanosomes, inflicting significant worldwide economic problems due to its adverse effects on meat and milk production. For diagnosis, most endemic countries continue to rely on traditional parasitological and serological techniques, such as the analysis of blood smears by microscopy and the Card Agglutination Test for T. evansi (CATT/T. evansi). Although these techniques suffer from a limited positive predictive value (PPV), resource constraints in endemic countries often hinder the adoption of more advanced diagnostic tools such as PCR. This paper addresses diverse diagnostic approaches for identifying T. evansi and assesses their viability in field settings. Moreover, it underscores the urgency of transitioning towards molecular diagnostic techniques such as Loop-Mediated Isothermal Amplification (LAMP) and Recombinase Polymerase Amplification (RPA) for dependable high-PPV point-of-care (POC) diagnostics. Finally, this review delves into strategies to enhance and refine next-generation diagnostics for Surra as part of a One Health approach.

Microscopic and serological survey of Trypanosoma evansi infection in Tunisian dromedary camels (Camelus dromedarius)

Camels are the most adapted species to the harsh ecosystems of the African continent where they represent 80% of world's population. However, they can be susceptible to many pathogens such as Trypanosoma evansi. This parasite is widely distributed in Africa and represents a real threat to animal health and production. In Tunisia, despite its importance, this disease is underestimated and only a few data are available. The present study aims to investigate the prevalence of the disease by combining microscopic and serological tests. A cross-sectional study was conducted on 307 dromedary camels randomly selected from Southern Tunisia. Collected blood samples were microscopically examined and tested with Card Agglutination Trypanosomiasis Test to detect anti-T. evansi antibodies. The microscopic and serological prevalence were estimated at 2.93 and 62.54%, respectively. Microscopic examination showed morphological features of T. evansi. All positives samples were collected from aged males (>5 years old). Seroprevalence was similar for both sexes but it was higher in dry season and in the southwest of Tunisia. The present study revealed high prevalence of T. evansi infection among dromedary camels. This highlights the need for adequate control measures based on the detection and treatment of infected animals and vector control. We recommend investigating the prevalence of infection in other domestic animals living in the same environment.

Molecular Analysis of Trypanosome Infections in Algerian Camels

PURPOSE

Surra is an economically important livestock disease in many low- and middle-income countries, including those of Northern Africa. The disease is caused by the biting fly-transmitted subspecies Trypanosoma brucei evansi, which is very closely related to the tsetse-transmitted subspecies T. b. brucei and the sexually transmitted subspecies T. b. equiperdum. At least two phylogenetically distinct groups of T. b. evansi can be distinguished, called type A and type B. These evolved from T. b. brucei independently. The close relationships between the T. brucei subspecies and the multiple evolutionary origins of T. b. evansi pose diagnostic challenges.

METHODS

Here we use previously established and newly developed PCR assays based on nuclear and mitochondrial genetic markers to type the causative agent of recent trypanosome infections of camels in Southern Algeria.

RESULTS/CONCLUSION

We confirm that these infections have been caused by T. b. evansi type A. We also report a newly designed PCR assay specific for T. b. evansi type A that we expect will be of diagnostic use for the community.

Prevalence and animal level risk factors associated with Trypanosoma evansi infection in dromedary camels

Surra is a non-cyclic parasitic disease caused by Trypanosoma evansi (T. evansi) and spread by biting flies. The disease has a severe impact on camel health, productivity, and market value, posing a significant threat to food safety and the economy. In a cross-sectional study, 370 blood samples were collected from camels in three Egyptian governorates. Samples were tested using parasitological (thin blood smear (TBS)), card agglutination test for T. evansi (CATT), and PCR to estimate the prevalence of T. evansi infection. Overall, the prevalence of T. evansi among examined camels was 17.3%, 18.9% and 22.7% using TBS, CATT and PCR methods, respectively. The risk of T. evansi infection in older camels (> 10 years) is higher than that in young ones (odds ratio (OR) = 9; 95% CI: 3.5–23.1), particularly during spring (OR = 2.5; 95% CI: 1.1–5.7). Furthermore, females and poor conditioned camels were 2.6 and four times more likely to get infection than males and good conditioned camels, respectively. The level of agreement between diagnostics tests were perfect kappa (> 0.83). Moreover, CATT showed higher sensitivity (0.83; 95% CI: 0.74–0.91) than TBS (0.76; 95% CI: 0.66–0.85) and both had perfect specificity (100%). In conclusion, our findings revealed a high rate of T. evansi infection in camels from the three Egyptian governorates. The CATT is a good test for routine use in control program of trypanosomiasis in camels.

Serological survey and associated risk factors' analysis of Trypanosomiasis in camels from Southern Tunisia

Surra (Trypanosoma evansi infection) is one of the main causes of dromedary (Camelus dromedarius) abortion, besides generating severe economic losses in herds. A sero-epidemiological survey was carried out between December 2018 and December 2019 in Southern Tunisia to estimate the seroprevalence of Trypanosoma evansi infection in camels and to determine its possible associated risk factors. Two-stage sampling was conducted to select breeders and camels targeted in our study. A total of 1205 blood samples were collected from 277 randomly selected farms belonging to six governorates of southern Tunisia. Sera were tested with the card agglutination test for Trypanosoma evansi (CATT/T. evansi) to detect the presence of anti-Trypanosoma. evansi antibodies. The overall individual and herd seroprevalence were 30.8% (95%CI 27.9–33.1%), 64.9% (95%CI 61.7–73), respectively. The seroprevalence of T. evansi infection both at the animal (26.2% (95%CI 21.4–30.9%) and herd level (84.4 (95%CI 76.3–92.5)) was higher in Kebili than in other governorates (P = 0.003). At the animal level, the infection rate with T. evansi was significantly associated to the age group among camels (P = 0.0008), production system (P = 0.006), bioclimatic stage (P = 0.02), and herd size (P = 0.04) in the univariable analysis. Multivariable logistic regression indicated that only age group and herd size were potential risk factors associated with Trypanosoma evansi infection. However, no significant variation of the seroprevalence of T. evansi with the sex of camels, farm type, and previous trypanocidal treatment were detected (P > 0.05). The findings of this study are crucial for this disease surveillance and control. Further investigations on the efficacy of the treatment against surra are needed to explain the persistence of the disease in the south of Tunisia.

Parasitological, serological, and molecular survey of trypanosomosis (Surra) in camels slaughtered in northwestern Nigeria

Surra is a parasitic disease caused by Trypanosoma evansi and transmitted non-cyclically by biting flies. The disease significantly affects the health, productivity, and market value of camels thereby constituting a major constraint to food safety, security, and economy. This is the first study on the prevalence of surra in northwestern Nigeria, using a range of diagnostic tests along the parasitological-serological-molecular continuum hence, emphasizing it as a major enzootic risk for camels in Nigeria. In this cross-sectional study, 600 blood samples were collected from camels at major abattoirs in northwestern Nigeria and evaluated for the prevalence of T. evansi using parasitological (Giemsa staining), serological (CATT/T. evansi), and molecular (VSG-PCR and sequencing) methods. The overall prevalence of surra recorded in this study was 5.3%, 11.5%, and 22.5% using Giemsa-stained blood smears, CATT/T. evansi, and VSG-PCR respectively. However, higher prevalence rates at 6.0%, 13.7%, and 26.7% by Giemsa-stained blood smears, CATT/T. evansi, and VSG-PCR were recorded in Katsina State compared with results from Kano State. A significantly (p < 0.05) higher prevalence by VSG-PCR was observed when compared with both parasitological and serological methods used. Although age and body condition scores were associated (p < 0.05) with surra prevalence in sampled camels, no seasonal association (p > 0.05) was recorded. Sequencing of the VSG region of Trypanosoma spp. Further confirmed the presence of T. evansi as the aetiological agent of surra from the sampled camels. Findings from this study call for the implementation of adequate control measures aimed at reducing the impact of T. evansi infections on camel production in Nigeria.

Review on trypanosomiasis and their prevalence in some country on the Red Sea

Trypanosomiasis is a protozoan infection affecting both human and animals in almost all parts of the world. It can affect a very large range of domestic and wild hosts including camelids, equines, cattle, buffaloes, sheep, goats, pigs, dogs and other carnivores, deer, gazelles and elephants. This review paper was designed to address the effect of this economically important disease in countries on the Red Sea, especially in Egypt, Sudan, Somalia, and Saudi Arabia during the period 2010 to 2020. The prevalence of trypanosomiasis is different between these countries due to different types of diagnostic methods (Giemsa-stained blood smears, Hematocrit centrifugation, Serological test, and molecular analysis PCR) used and differential distribution of vector (Tse tse) flies. In current review, retrospective studies of published literature on distribution and prevalence of Trypanosoma evansi infection in the Red Sea Countries was conducted [Google Scholar and PubMed were used to retrieve the published literature from 2000-2020. A total of 77 published articles met the eligibility criteria and were reviewed. A total of 16 reports have been reported on the prevalence and distribution of Trypnosoma evansi infection in the Red Sea Countries have been from 2010-2020]. According to the published literature, we can say that trypanosomiasis in camels are more prevalent in Sudan than in other countries, followed by 17% and 51.78% in both clinical and non-clinical cases. Hence, the reliable diagnostic tests should be used for rapid treatment or control of the disease as if not treated appropriately in early-stage, can lead to death of the camels.

Seroprevalence and risk factors for Trypanosoma evansi, the causative agent of surra, in the dromedary camel (Camelus dromedarius) population in Southeastern Algeria

Surra, caused by Trypanosoma evansi, is a re-emerging animal trypanosomosis, which is of special concern for camel-rearing regions of Africa and Asia. Surra decreases milk yield, lessens animal body condition score and reduces market value of exported animals resulting in substantial economic losses. A cross-sectional seroprevalence study of dromedary camels was conducted in Algeria, and major risk factors associated with infection were identified by collecting data on animal characteristics and herd management practices. The seroprevalence of T. evansi infection was determined in sera of 865 camels from 82 herds located in eastern Algeria using an antibody test (card agglutination test for Trypanosomiasis – CATT/T. evansi). Individual and herd seroprevalence were 49.5% and 73.2%, respectively, indicating substantial exposure of camels to T. evansi in the four districts studied. Five significant risk factors for T. evansi hemoparasite infection were identified: geographical area, herd size, husbandry system, accessibility to natural water sources and type of watering. There was no association between breed, sex or age with T. evansi infection. Results of this study provide baseline information that will be useful for launching control programmes in the region and potentially elsewhere.

Assessment of Trypanosoma evansi prevalence and associated risk factors by immune trypanolysis test in camels from Ghardaïa district, southern Algeria

Trypanosoma evansi (T. evansi) is a flagellated parasite with worldwide distribution, mainly affecting camels, horses, dogs, buffaloes and wild animals. Trypanosomosis caused by T. evansi, known as surra, is a vector borne disease that affects the health and productivity of camels. The aim of our study was to assess the prevalence of trypanosomosis due to T. evansi in camels by the immune trypanolosis test and to identify associated risk factors. Our cross-sectional study was performed on 161 camels from Ghardaïa district, southern Algeria. A structured questionnaire was used to collect data on individual characteristics (age, gender and breed) husbandry management (herd size and activity of animals) and health conditions (history of abortion and clinical symptoms). The immune trypanolysis test revealed an overall seroprevalence of 9.3% (CI 95%, 5.9-14.9). Possible factors associated with T. evansi infection were analysed by univariate and multivariate logistic regression. The results showed that risk factors for camels were history of symptoms (P = 0.002, OR = 21.91, CI95% = 3.48-169.80), racing activities (P = 0.003, OR = 0.01, CI95% = 0.001-0.18) and small herd size (P = 0.013, OR = 8.22, CI95% = 1.64-49.75). In conclusion, this study showed that T. evansi is endemic in camels of Ghardaïa district. To reduce dissemination of the disease to non-endemic areas, it is recommended to minimise risk factors associated with the infection.

Comparison of serological and molecular tests for detection of Trypanosoma evansi in domestic animals from Ghardaïa district, South Algeria

Trypanosoma evansi (T. evansi) is a hemoflagellate parasite that affects a broad range of mammalian hosts and that causes a disease called surra. Diagnosis of surra based on clinical symptoms alone is inaccurate. Therefore, a variety of serological and molecular diagnostic tests are used to assist in the detection of T. evansi infections. The aim of this study was to compare the diagnostic performance of four serological tests (CATT/T.evansi, immune trypanolysis, ELISA with purified variant surface glycoprotein RoTat 1.2 and with whole cell lysate) and two molecular PCR tests targeting sequences within the ribosomal genes locus (ITS1 TD PCR and 18S qPCR). Tests were carried out on blood samples from 161 dromedary camels, 93 horses, 129 goats, 168 sheep, 127 bovines and 76 dogs. Latent class analysis was carried out to calculate the sensitivity and specificity of each diagnostic test. Cohen's Kappa test was used to assess the concordance between the different diagnostic tests. Overall positivity rates observed with the serological tests were as follows: 3.1 % with CATT/T.evansi, 4.9 % with ELISA/RoTat 1.2, 3.4 % with ELISA/whole lysate and 2.0 % with immune trypanolysis (TL). Among the 754 samples tested with the molecular tests, 1.7 % were positive with 18S qPCR and 1.3 % with ITS1 TD PCR. Cohen's Kappa test showed agreement ranging from fair to substantial (k = 0.2-0.8) between serological diagnostic tests. However, it showed a perfect agreement (k = 0.868) between molecular diagnostic tests. Latent class analysis showed that all serological tests were 100 % sensitive, in contrast to the molecular tests with 47 % sensitivity. All tests, though, were highly specific (≥ 97 %). Given the persistence of circulating antibodies after cure, detectable by serological tests, it is recommend combining a serological and a molecular diagnostic test for accurate diagnosis of infection with T. evansi in domestic animals.

Epidemiological investigations on Trypanosoma evansi infection in dromedary camels in the South of Algeria

An epidemiological study of Trypanosoma evansi (T. evansi) infection in dromedaries was conducted in four wilayate (localities) of Southern Algeria: Béchar, El Bayadh, Ouargla, Tamanrasset. Between February 2014 and April 2016, 1056 camels of different ages and both sexes from 84 herds were sampled. The prevalence was determined through parasitological examination (Giemsa stained thin smear, GST), serological tests (CATT/T. evansi, ELISA/VSG RoTat 1.2, immune trypanolysis), and molecular tests (T. evansi type A specific RoTat 1.2 PCR and T. evansi type B specific EVAB PCR). The overall prevalence was 2.4 % with GST, 32.4% with CATT/T. evansi, 23.1% with ELISA/VSG RoTat 1.2, 21.0% with immune trypanolysis (TL), 11.2 % with RoTat 1.2 PCR and 0% with EVAB PCR. El Bayadh was the most affected wilaya with 11.8% positives in GST, 74.9% in CATT/T. evansi, 70.1% in ELISA/VSG RoTat 1.2 and 62.2% in immune trypanolysis. Only in Béchar, a non-significantly higher prevalence (13.6%) was observed with RoTat1.2 PCR than in El Bayadh (13.0%). We didn't find any evidence of the presence of T. evansi type B in the study area.

Prevalence and distribution of Trypanosoma evansi in camels in Somaliland

The prevalence and distribution of Trypanosoma evansi (T. evansi) infection on camels in Somaliland were studied using the card agglutination test (CATT/T. evansi). A total of 2575 camels were surveyed. The overall animal-level apparent (test) prevalence in Somaliland was 26.4%. The prevalence was highest in the Sahil Region (37.3%) followed by Togdheer (28.4%), Sanaag (27.4%), and Sool (26.2%). There was a significant difference in the seroprevalence between the regions (χ² = 35.2, df = 1, P < 0.001) with the prevalence being significantly higher in Sahil than in Woqooyi Galbeed and Awdal, respectively. Camels from the eastern districts were two times more likely to be infected than camels from the western districts (P < 0.001). Herds in the coastal area were also more likely to be infected (37.0%) than herds from the inland areas (26.9%).The seroprevalence varied significantly between body condition score groups (P < 0.001) with the highest seroprevalence in camels of poor body condition (39.5%) and the lowest in camels of good body condition (18.4%) score. Animals in poor body condition were almost three times more likely to be positive than animals in good body condition (OR = 2.9; 95% CI 2.2, 3.8).

Systematic review and meta-analysis on the global distribution, host range, and prevalence of Trypanosoma evansi

BACKGROUND

Surra is an animal trypanosomosis, caused by infection with Trypanosoma evansi and leading to severe economic loss due to mortality and morbidity. Compared to tsetse-transmitted animal trypanosomoses, little attention is given to the epidemiology and control of surra. Understanding its epidemiology is a first step in local and global efforts to control the disease. We conducted a systematic review and meta-analysis of published studies on distribution, host ranges and prevalence of T. evansi infection.

METHODS

Four electronic databases were searched for publications on T. evansi that met our inclusion criteria for the systematic review. Subsets of publications were subjected to meta-analysis for the pooled prevalence of T. evansi in various hosts as determined by multiple detection methods.

RESULTS

A total of 272 references published between 1906-2017 were included. Trypanosoma evansi was reported from 48 countries; largely confined to Africa and Asia with publications on natural T. evansi infections from 77% (n = 48) of countries, contrasting with seven countries in South America, and four in Europe where T. evansi is not endemic but was imported with infected animals. Although surra is a notifiable disease, many countries do not report surra cases to OIE. Trypanosoma evansi was mainly reported from dromedary camels in Africa and the Middle East, water buffaloes, cattle, dogs and horses in East and Southeast Asia. In South America, the acute form of the disease was reported in horses and dogs. Surra was also reported in a wide range of wild animals. Some rare human cases occurred in India and Vietnam. Meta-analysis on a subset of 165 publications indicated pooled prevalence of T. evansi in domestic animals ranging from 14-31%, 6-28% and 2-9% using respectively antibody detection, molecular and parasitological tests, with camels as the most affected, followed by buffalo and cattle.

CONCLUSIONS

This study illustrates that T. evansi affects a wide range of domestic and wild animals in Africa, Asia and South America with highest prevalence observed in dromedary camels. For successful control of T. evansi, both locally and globally, the role of wild animals in the epidemiology of surra needs further investigation.

Trypanosoma evansi infection and major risk factors for Iranian one-humped camels (Camelus dromedarius)

Trypanosoma evansi is a cosmopolitan protozoan which affects camelids and may cause illness and economic losses. The present study was aimed to determine the prevalence and geographic distribution of T. evansi in Iranian one-humped camels of South East Iran. A total of 369 camels were randomly examined from three parts of southeastern Iran from March to September 2015. Blood samples were taken from jugular vein and examined by using thin blood smear and mercuric chloride test. Ninety-five out of 369 examined camels (25.75%) with clinical signs (15.8%, 58/369) were found to be infected with T. evansi. The prevalence was significantly higher in camels more than 4 years-old (23.3%) with clinical signs (8.8%) than the other ones. There was no significant difference between the prevalence and sex (6.23% male and 19.51% female). Trypanosoma evansi infection was geographically found in all investigated regions with the highest prevalence in North (17.61%). The results indicated that T. evansi infection was prevalent in Iranian one-humped camels which could be useful finding to lunch control programs in the region.

The role of Nucularia perrinii Batt. (Chenopodiaceae) in the camel-based Sahrawi social-ecological system

BACKGROUND

Pastoral social-ecological systems (SESs) are adaptive and complex systems rooted in the extensive exploitation of forage plants for livestock-based livelihoods and culture. There are species and relations that are foundational to the existence of these SESs. Nucularia perrinii Batt. (Chenopodiaceae) is an endemic halophyte plant of central and western Sahara seldom cited in the scientific literature. The objective of this study was to investigate the role of this plant in the SES of the Sahrawi camel nomads of Western Sahara.

METHODS

The data analyzed were collected in the Sahrawi refugee camps of Algeria and in Western Sahara between 2006 and 2010. Fieldwork included semi-structured (n = 38) and retrospective (n = 12) interviews with Sahrawi refugees, nomads, and camel owners about N. perrinii and associated topics (e.g. distribution, importance for camels, camel diseases, associated grazing practices, other forage plants, etc.).

RESULTS

Askaf, as the Sahrawi call the plant, is crucial to camels' survival, providing salts and water even during dry spells. It holds a pivotal role in the Sahrawi culture, defining the geographical boundaries of the Sahrawi SES and relating the grazing territory with the taste it gives to camel milk, which support the inclusion of askaf as a main element of Sahrawi cultural identity.

CONCLUSIONS

We argue that N. perrinii ties the ecology of the western Sahara desert with camel husbandry and associated livelihoods, and further with the culture and worldview of the Sahrawi nomads. We stress the keystone role that some forage plants may have in extensive pastoral SESs worldwide.

Ethnoveterinary of Sahrawi pastoralists of Western Sahara: camel diseases and remedies

BACKGROUND

Pastoral populations around the world hold complex and detailed ethnoveterinary knowledge, essential for the survival of their herds and securing their livelihood. In recent decades, several studies have given attention to local veterinary remedies and practices and their validation, and to the local conceptualization of livestock diseases. Despite this, relatively little has been reported on indigenous knowledge of camel diseases (e.g., aetiological factors, epidemiological patterns, symptoms, prevention and treatments). This paper focuses on the traditional knowledge of camel diseases and their treatments among Sahrawi nomads, detailing how this knowledge is powerfully reflected on pastoral adaptation strategies to the ecological system of Western Sahara.

METHODS

Between 2005 and 2010, freelisting exercise on camel diseases with 46 Sahrawi nomads and refugees, semi-structured interviews with 36 knowledgeable informants about camel diseases and associated treatments, and a voucher specimen collection of the plants and products cited were conducted in the territories administered by the Saharawi Arab Democratic Republic, Western Sahara. Analytical methods included standard ethnobiological, ethnobotanical and cultural consensus analyses.

RESULTS

In total, 42 camel diseases were freelisted by informants, with four (i.e., mange, dermatomycosis, respiratory infections, and mastitis) found to be culturally highly salient. These four represent the most common veterinary conditions experienced by Sahrawi pastoralists. In addition, 42 plant species belonging to 22 botanical families (Hammada scoparia, Acacia tortilis, Zygophyllum gaetulum, Nucularia perrinii, and Panicum turgidum among the species most used) were listed as used in the treatment of these diseases, as well as about 30 remedies of animal (e.g., from camels, donkeys, and/or spiny-tailed lizards) and mineral origin, and of cauterizations.

CONCLUSIONS

This study provides an overall picture of the most important camel diseases and remedies as reported by Sahrawi informants, detailing how the vast knowledge that the Sahrawi hold on the health and disease of their camels is constructed through contrasts between their customary nomadic land (and associated climate, soils, grazing and therapeutic resources) and the surrounding areas (and associated diseases), which are traditionally used only in cases of drought.

Trypanosome infection in dromedary camels in Eastern Ethiopia: Prevalence, relative performance of diagnostic tools and host related risk factors

A cross-sectional study was conducted in Chifra and Dewe districts of Afar region, Eastern Ethiopia, to determine the prevalence, agreement between diagnostic tests and host related risk factors of trypanosome infection in camel. An overall prevalence of 2%, 24.1%, 21.3%, 9.5% and 7.8% was recorded with respectively Giemsa stained thin blood smear, CATT/T. evansi, RoTat1.2 PCR, 18S PCR and ITS-1PCR in a cohort of 399 animals. Only one T. vivax infection was confirmed by TvPRAC PCR indicating T. evansi as the predominant species affecting camels in the study area. No single animal was positive when tested with T. evansi type B specific EVAB PCR. There was slight agreement between the CATT/T. evansi and the molecular tests. Among the PCR methods, RoTat 1.2 PCR yielded a significantly higher positivity rate compared to 18S PCR and ITS-1 PCR. There was no significant difference in the positivity rate observed in each gender of camels (p>0.05). The positivity rate was significantly higher in camels with poor body condition and in older animals when tested using the CATT/T.evansi or RoTat 1.2 PCR (p>0.05). Camels that tested positive with all tests had significantly lower PCV's (p<0.05). This study provides further evidence that T. evansi is endemic in the Afar region of Ethiopia. The latent class analysis indicated an estimate overall prevalence of 19% (95% CI: 13-28). Moreover, the model indicated low sensitivity of CATT/T. evansi (43%) and the PCR tests (39-53%) but higher specificity of the PCR tests (86-99%) and low specificity of CATT/T. evansi (80%). This study suggests that improved sensitivity and reliability of the tests would help diagnosis of trypanosomosis. Further studies are required to determine the prevalence of clinical disease and losses due to trypanosomosis.

Trypanosoma evansi and surra: a review and perspectives on transmission, epidemiology and control, impact, and zoonotic aspects

This paper reviews the transmission modes of Trypanosoma evansi. Its worldwide distribution is attributed to mechanical transmission. While the role of tabanids is clear, we raise questions on the relative role of Haematobia sp. and the possible role of Stomoxys sp. in delayed transmission. A review of the available trypanocidal drugs and their efficacy in various host species is useful for understanding how they interact in disease epidemiology, which is complex. Although there are similarities with other mechanically transmitted trypanosomes, T. evansi has a more complex epidemiology due to the diversity of its hosts and vectors. The impact of clinical and subclinical disease is difficult to establish. A model was developed for buffaloes in the Philippines, which could be transferred to other places and livestock systems. Since Trypanosoma evansi was reported in humans, further research is required to investigate its zoonotic potential. Surra remains a potentially emerging disease that is a threat to Australia, Spain, and France. A number of questions about the disease have yet to be resolved. This brief review of the basic knowledge of T. evansi suggests that there is renewed interest in the parasite, which is spreading and has a major economic impact.

Prevalence of Trypanosoma evansi in camels using molecular and parasitological methods in the southeast of Iran, 2011

Surra is caused by infection with the protozoal parasite, Trypanosoma evansi. This parasite was transmitted mechanically by biting flies which is widespread in camels in the world. The aim of this study is to determine the prevalence of T. evansi in camels in Rafsanjan, Kerman province, southeast of Iran. In this study, 95 suspected camels were randomly selected in 2011. Blood samples were taken from deep blood vessels. Thin and thick blood smears were prepared in laboratory. Blood smears were stained by Giemsa and studied under a light microscope. The positive blood samples were also used for further molecular analysis. Data were analyzed using SPSS 17.0 software and P ≤ 0.05 was considered as statistical difference. A total of 95 camels were examined for infection with T.evansi using parasitological and molecular methods. The overall prevalence of infection was 2.1 %. It was found that the frequency of infection was significantly higher (P < 0.05) in age group >6 years old than the corresponding younger camels. However, there was no significant difference when the gender was considered. PCR technique confirmed the two infected cases were T. evansi. Results of the present study indicated that surra is present in Rafsanjan county, Kerman province in an infection rate of 2.1 % in camels. To our knowledge, this is the first study reported from this province. Further investigations are needed to focus on vectors and to evaluate the risk factors.

Epidemiology of Trypanosoma vivax infection in cattle in the tse-tse free area of Lake Chad

A study was conducted in Chad to estimate the prevalence and the incidence of Trypanosoma vivax infection in herds of cattle from the Lake Chad area. The risk factors associated with disease were also identified. A random sample of 933 cattle from 17 herds was initially selected (January 1999, cold dry season). Cattle were identified by ear-tags and sampled in the rainy season (July 1999) and the cold dry season (January 2000). Each animal sampled was treated with diminazene aceturate (3.5mg/kg). Samples were examined for the presence of T. vivax using an antibody (indirect ELISA) and a parasite detection test (buffy-coat technique, BCT). Standardized questionnaires with information about the host and management practices were collected and evaluated for their association with seroprevalence (model 1) and parasitological prevalence (model 2) as indicator of host susceptibility to T. vivax infection. Risk factors were selected using two approaches: ordinary logistic regression (OLR) and generalized estimating equations (GEE) to account for within-herd correlation. The apparent prevalence was 1.6% using BCT and 42.3% with indirect ELISA. The true prevalence in the sample was estimated to (2.0%-8.0%) with two assumptions of BCT sensitivity. Overall, 58.8% (BCT) and 100.0% (ELISA) of the herds had a least one-positive animal. In January-July 1999, apparent monthly incidence was calculated at 0.24% in comparison with 0.76% for August 1999-January 2000. The true monthly incidence was estimated at 0.36%-1.43% for the first period and at 0.94%-3.78% for the second period. Risk factors associated with seroprevalence were age, race, a great number of small ruminants in the herd, and latitude and longitude of pasture area in the rainy season. Risk factors associated with BCT prevalence were duration of seasonal migration and longitude of pasture area in the rainy season. In conclusion, T. vivax is present and widely disseminated in the cattle herds of tse-tse free area of Lake Chad. Farm-level factors, particularly seasonal migration, should be considered as the main risk factors for infection and to host susceptibility to the parasite.

A simple and rapid method for detection of Trypanosoma evansi in the dromedary camel using a nested polymerase chain reaction

A nested polymerase chain reaction (nPCR)-based assay, was developed and evaluated for rapid detection of Trypanosoma evansi in experimentally infected mice and naturally infected camels (Camelus dromedarius). Four oligonucleotide primers (TE1, TE2, TE3 and TE4), selected from nuclear repetitive gene of T. evansi, were designed and used for PCR amplifications. The first amplification, using a pair of outer primers TE1 and TE2, produced a 821-bp primary PCR product from T. evansi DNA. The second amplification, using nested (internal) pair of primers TE3 and TE4, produced a 270-bp PCR product. T. evansi DNAs extracted from blood samples of experimentally infected mice and naturally infected Sudanese breed of dromedary camels were detected by this nested PCR-based assay. The nested primers TE3 and TE4 increased the sensitivity of the PCR assay and as little as 10 fg of T. evansi DNA (equivalent to a single copy of the putative gene of the parasite) was amplified and visualized onto ethidium bromide-stained agarose gels. Amplification products were not detected when the PCR-based assay was applied to DNA from other blood parasites including Thieleria annulata, Babesia bigemina or nucleic acid free samples. Application of this nPCR-based assay to clinical samples resulted in direct detection of T. evansi from a variety of tissue samples collected from experimentally infected mice and blood from naturally infected camels. The described nPCR-based assay provides a valuable tool to study the epidemiology of T. evansi infection in camels and other susceptible animal populations.

Evaluation of Diagnostic Tests for Trypanosoma evansi in Experimentally Infected Pigs and Subsequent Use in Field Surveys in North Vietnam and Thailand

This study is concerned with the evaluation of established diagnostic tests for diagnosis of Trypanosoma evansi in pigs. The immune trypanolysis test (TL), card agglutination test (CATT), latex agglutination test (LATEX), enzyme-linked immunosorbent assay (ELISA), microhaematocrit centrifugation technique (MHCT) and mouse inoculation (MI) tests were initially evaluated in experimentally infected fattening pigs. All infected pigs were confirmed parasitologically positive with both MHCT and MI. Results of the serological assays indicated that the TL could be a reference test for the presence of RoTat 1.2 antibodies in pigs. The results of the CATT and LATEX were inconsistent with the TL while the ELISA results correlated with the TL results. The four serological assays were subsequently used in two field surveys in Vietnam and Thailand. Results of the two agglutination assays (CATT and LATEX) were not consistent and did not correlate with TL results. The ELISA at percentage positivity of 22 appeared to have good ability to discriminate between seropositive and seronegative animals. Of the 437 samples collected at smallholder pig premises in northern Vietnam, no positive pigs were detected with the TL test. In Thailand, 77 samples were collected from five farrowing farms with a history of surra. Two parasitologically positive sows were found and on each farm seropositive sows were detected.

Trypanosoma equiperdum: master of disguise or historical mistake?

After 100 years of research, only a small number of laboratory strains of Trypanosoma equiperdum exists, and the history of most of the strains is unknown. No definitive diagnosis of dourine can be made at the serological or molecular level. Only clinical signs are pathognomonic and international screening relies on an outdated cross-reactive serological test (the complement-fixation test) from 1915, resulting in serious consequences at the practical level. Despite many characterization attempts, no clear picture has emerged of the position of T. equiperdum within the Trypanozoon group. In this article, we highlight the controversies that exist regarding T. equiperdum, and the overlap that occurs with Trypanosoma evansi and Trypanosoma brucei brucei. By revisiting the published data, from the early decades of discovery to the recent serological- and molecular-characterization studies, a new hypothesis arises in which T. equiperdum no longer exists as a separate species and in which current strains can be divided into T. evansi (the historical mistake) and Trypanosoma brucei equiperdum (the master of disguise). Hence, dourine is a disease caused by specific host immune responses to a T. b. equiperdum or T. evansi infection.

Detection of Trypanosoma evansi in camels using PCR and CATT/T. evansi tests in Kenya

Camel trypanosomosis (Surra) causes high morbidity and is an impediment to the camel husbandry in Kenya. The lack of a sensitive diagnostic test has hindered the collection of accurate epidemiological data and institution of control programmes. A cross-sectional study was conducted in three districts of Kenya to estimate the prevalence of Trypanosoma evansi (T. evansi) and to compare four diagnostic tests: polymerase chain reaction (PCR), card agglutination test (CATT/T. evansi), microhaematocrit centrifugation technique (MHCT) and mouse inoculation (MI). A total of 549 camels were randomly sampled. The overall prevalence of Surra was 5.3% using MHCT, 26.6% using PCR and 45.9% using CATT/T.evansi. There was a significant difference (P < 0.001) between PCR and CATT/T.evansi test, MHCT and MI in detection of T. evansi. The prevalence of T. evansi was 39.8% in Samburu, 24.7% in Nanyuki and 14.4% in Isiolo districts using PCR. A male camel was 2.6 times more likely to be infected with T. evansi compared to a female camel (OR = 3.0% CI: 1.6, 4.1), while an adult camel was 2.2 times more likely to be infected compared to non-adults (OR = 2.2; 95% CI: 1.2, 5.0). There was a poor association between the presence of the published clinical signs and seropositivity (kappa = 0.12), PCR (kappa = 0.11) and MHCT (kappa = 0.05). However, there was a higher agreement between farmers' classification of disease with the PCR test (kappa = 0.5, n = 61). The mean PCV varied with age, presence of infection, locality and gender, with the lowest mean PCV being recorded in MHCT-positive animals (20.97 +/- 0.5) and from infected calves (19.5 +/- 1.2). This study shows that PCR was more sensitive in detecting T. evansi than other tests used. Further, the prevalence of T. evansi in the camel herds sampled is higher than that previously reported in Kenya, and that the judgment by camel keepers may be a reliable "pen-side" diagnostic test for Surra. Considering the low sensitivity of parasitological techniques in detection of chronic T. evansi infection and high cost of PCR, development of a sensitive pen side diagnostic test, with a low cost is still a priority.

Prevalence of Trypanosoma evansi infection and associated risk factors in camels in eastern Chad

A cross-sectional study was conducted to estimate the prevalence of Trypanosoma evansi infection (Surra) in herds of camels from the eastern area of Chad. The risk factors associated with disease were also identified. From August 1997 to April 1998, a random sample of 2831 camels from 136 herds was selected. Blood samples were collected and examined for the presence of T. evansi using an antibody (card agglutination test-CATT/T. evansi) and a parasite detection test (buffy-coat technique-BCT). Standardized questionnaires with information about the host and management practices were collected and evaluated for their association with seroprevalence (model 1) and parasitological prevalence (model 2) as indications of host sensitivity. In both models, risk factors were selected using ordinary logistic regression (OLR) and herd effect was evaluated using a generalized estimating equations (GEE) model. The apparent prevalence was 5.3% using BCT and 30.5% with CATT. Real prevalence was estimated at 16.9% +/- 1.4 (alpha = 5%). Overall, 27.9% (BCT) and 94.9% (CATT) of the herds had a least one-positive animal. Real herd prevalence was estimated at 42.6 +/- 8.3% (alpha = 5%). Camels of the large transhumants had the highest prevalence (estimated to 30.3% +/- 2.5; 62.9 +/- 12.0 in herds). Risk factors associated with seroprevalence were age, ethnic group, length of seasonal migration and longitude of pasture area in the dry season. Risk factors associated with BCT prevalence were age, length of seasonal migration, longitude of pasture area in the dry season, latitude of pasture area in the rainy season and season of sampling.

Camel trypanosomosis in Morocco. 2. A pilot disease control trial

A first epidemiological study on camel trypanosomosis was conducted in 1997 and 1998 in five Moroccan Saharan provinces. It revealed two major foci at Merzouga (Tafilalet province) and Zagora (Ouarzazate province) where tour camel seroprevalences were 35.4 and 43.3%, respectively, for each region. The first area was chosen in the present study as a pilot region for a control program based on epidemiological data with the aim of evaluating the efficiency of the trial in terms of seroconversion, incidence and health condition. After finding the endemic focus at Merzouga, four other field studies were organised in this area, at 4-month intervals, in order, firstly, to control the camel reservoir by treating all the camels found in the region during the visit using melarsomine (Cymelarsan, Rhône-Mérieux, the only trypanocide registered in Morocco), and, secondly, to collect blood samples for studying temporal changes in seroprevalence as well as in anaemia rate. All the 291 tour camels of the area, that were present in at least one of the field visits were examined and included in the trial. Among them, 162 were treated once, 84 twice and 41 three times. A total of 676 serum samples were collected from these camels. At the end of the trial--1 year later--seroprevalence had dropped from 58% (May 1998) to 19% and the mean Ab-ELISA value had decreased from 0.52 (before treatment) to 0.12 (which is below the threshold level), after the third campaign. The haematocrit of the animals was also slightly improved, indicating that trypanosomosis was a major cause, but it was not the only incriminated factor. A seasonal effect was observed. The overall seroprevalence was reduced between spring 1999 and summer 1999, without treatment, whereas a negative effect was recorded on packed cell volume, more camels being found anaemic in summer than in spring. The application of these strategic treatments was associated with a large reduction in the seroprevalence of trypanosomosis, but there was no complete eradication because of the continual exchange of animals from other foci such that of Zagora. The overall seroconversion after 1 year reached 55% and no post-treatment complication was recorded, whereas the incidence due to new infections approached 4.3%. Moreover, several factors like the unusual way of life of the dromedaries, including stress, excessive work, overcrowding and continual contact with other animals coming from other infected regions contribute to the persistence of the disease.

Evaluation of antigen and antibody rapid detection tests for Trypanosoma evansi infection in camels in Kenya

The card agglutination test for Trypanosoma evansi (CATT/T. evansi) for the detection of antibodies, and Suratex for the detection of circulating antigens were compared in a cross-sectional study involving camels in eastern and central parts of Kenya. Of the 2227 camels screened, 2038 were owned by nomadic pastoralists in T. evansi endemic areas in eastern Kenya. A herd of 86 camels were from a ranch in Mugwoni. In Athi River area, 35 camels belonged to Kenya Trypanosomiasis Research Institute, and 68 were slaughter animals. Diagnostic sensitivity estimates were obtained by testing sera from 51 camels that had been found to be parasitologically positive by the haematocrit centrifugation technique, buffy-coat technique and mouse inoculation. Diagnostic specificity was estimated by testing sera from 35 camels known to be trypanosome-free. Positive and negative predictive values (NPVs) were calculated using a range of prevalence values. The sensitivity of CATT/T. evansi (68.6%) was higher than that of Suratex (58.8%), but not significantly. Both tests had equally high specificity (100%). The overall prevalence was 2.3% (51 out of 2227) by parasite detection, 32.2% (327 out of 1017) by CATT/T. evansi and 19.6% (188 out of 961) by Suratex. Overall, there was a positive association between CATT/T. evansi and Suratex though the strength of association was low (McNemar's test=46.12, P=0.001; kappa=0.26, CI: 0.20-0.33). Parasite prevalence ranged from 0% in several herds to 27.8% in a herd in Isiolo. Prevalence was highest in Isiolo with 2.5% (51 out of 2030) by parasitological detection, 38.8% (321 out of 828) by CATT/T. evansi and 21.9% (169 out of 772) by Suratex. In Mugwoni prevalence was 7 and 18% by CATT/T. evansi and Suratex, respectively, and no parasites were detected. In Athi River Suratex detected 2.9% (3 out of 103) positive while CATT/T. evansi and parasitological methods gave negative results. At prevalence values between 10 and 100%, CATT/T. evansi as well as Suratex had infinitely high positive predictive values, whereas Suratex had a lower NPV than CATT/T. evansi. In conclusion, results of this study showed that CATT/T. evansi and Suratex were able to detect aparasitaemic infections rapidly and were more sensitive than parasitological methods in revealing the true extent of trypanosomosis in a herd. The tests effectively complemented parasitological methods in the detection of T. evansi infections in camels.

Camel trypanosomosis in Morocco 1: results of a first epidemiological survey

An epidemiological survey of camel trypanosomosis was conducted for the first time in Morocco in 1997 and 1998. Five provinces located in the south and southeast of the High Atlas mountain chain were included in this study. A total number of 1460 serum samples were collected and tested by a card agglutination test for trypanosomosis (CATT) and enzyme-linked immunosorbant assay (Ab-ELISA) to detect anti-Trypanosoma evansi antibodies. The overall seroprevalence was 14.1% by CATT and 18.2% by Ab-ELISA. Two very active foci were identified in Zagora and Merzouga with high Ab-ELISA prevalences of 43.3 and 35.4%, respectively, for each area. The concordance between the CATT and Ab-ELISA was 94.1%. The age-related distribution of seroprevalence showed a tendency for the infection rate to increase with age up to a maximum in the 7-10 year-old group. Clinical examination revealed that enlargement of lymph nodes was the most frequent sign in seropositive animals (79.7%). The comparison of haematocrit values of seropositive and seronegative animals showed a significant difference that indicated severe anaemia in infected animals. Isolation of the parasite by inoculation of mice allowed us to collect 15 T. evansi isolates from Zagora and three from Merzouga. The study showed that the Saharan provinces of Morocco were slightly affected by camel trypanosomosis but two hyperendemic foci, Zagora and Merzouga, were found to be sources of contamination for the surrounding regions.

General expression of RoTat 1.2 variable antigen type in Trypanosoma evansi isolates from different origin

The variable surface glycoprotein of Trypanosoma evansi RoTat 1.2 variable antigen type (VAT) is used as an antigen in different antibody detection assays for T. evansi. To obtain more information on the predominant character of RoTat 1.2 and its diagnostic potential in antibody detection tests, we checked its expression in 10 different T. evansi stocks and clones from different parts of the world. Cryostabilates were injected into mice and the trypanosomes of the first peak parasitaemia were screened for the presence of RoTat 1.2 by VAT specific immunofluorescence. To monitor the appearance of RoTat 1.2 specific antibodies during infection, rabbits were infected and serologically tested at different time intervals with VAT specific immune trypanolysis, CATT/T. evansi, LATEX/T. evansi and ELISA/T. evansi. Test results confirm the predominant character of RoTat 1.2.

Ten years of research activities on tropical parasitology of dromedaries, cattle, and small ruminants in Mauritania

In the past, the essential part of the activity of the parasitology laboratory of the Centre National d'Elevage et de Recherches Vétérinaires (CNERV) was represented by diagnostic work that enabled the construction of an inventory of local parasitic fauna and a good collection of specimens. However, the small and irregular number of samples each year, led us to switch our activities in 1990 toward work that could better justify the existence of CNERV. We started work on applied research topics, such as tick-borne diseases, helminthology (nemathelminths and plathelminths), and trypanosomosis. These results were valorized through scientific publication and communication at international meetings. The most valuable information was conveyed to herders.

Incidence, biochemical and haematological alterations induced by natural trypanosomosis in racing dromedary camels

In this study 10.67% incidence of trypanosomosis was observed in 150 racing camels by Suratex (latex agglutination). A significant decrease (P<0.05) in RBC, Hb, PCV and lymphocyte was observed, while a significant (P<0.05) increase in WBC and neutrophils was noted in trypanosomosis positive samples. The blood chemistry parameters indicated that there was significant (P<0.05) decrease in iron and albumin, but no significant alteration was observed in alkaline phosphatase (ALP), alanine aminotransferase (ALT), asparate aminotransferase (AST), gamma glutamyltransferase (GGT), lactic dehydrogenase (LDH), urea, total protein, calcium, creatinine, phosphorous and magnesium.

Comparison of serological tests for Trypanosoma evansi natural infections in water buffaloes from north Vietnam

In the present study, a collection of 415 water buffalo serum samples originating from the north of Vietnam was used for evaluation of different diagnostic antibody detection methods available to detect infections with Trypanosoma evansi. The diagnostic sensitivity and specificity of a direct card agglutination test (CATT/T. evansi), an indirect card agglutination test (LATEX/T. evansi) and a newly developed antibody detection ELISA (ELISA/T. evansi) was calculated on the basis of parasitological results, obtained by mouse inoculation, and compared for all assays. The immume trypanolysis assay with the predominant T. evansi RoTat 1.2 variable antigen type was used as reference test for antibody presence. All parasitologically confirmed animals (n=8) were positive in all tests. Diagnostic specificity was highest in CATT/T. evansi (98%) followed by the ELISA/T. evansi (95%) and the LATEX/T. evansi (82%). Concordance of the variant specific immune trypanolysis test with the other tests was calculated and revealed that few (1-8%) false positive results were actually due to a specific reactions, and that LATEX/T. evansi and ELISA/T. evansi detected more immune trypanolysis positives than the CATT/T. evansi. It was concluded that, apart from the immune trypanolysis test, which is not generally applicable, ELISA/T. evansi with a 30% positivity cut-off and LATEX/T. evansi, thanks to their superior capacity of detecting T. evansi specific antibodies, would be suitable as epidemiological tools detecting both active infections and persisting T. evansi specific antibodies. The ELISA/T. evansi with a 50% positivity cut-off and the CATT/T. evansi on the other hand, seem more appropriate to detect true infected water buffaloes.

Camel trypanosomosis in the Canary Islands: assessment of seroprevalence and infection rates using the card agglutination test (CATT/T. evansi) and parasite detection tests

Trypanosomosis due to Trypanosoma evansi (surra) is a major enzootic disease of the dromedary camel. Thus, the purpose of the present study was to assess seroprevalence and infection rates in the Canary Islands using antibody(-card agglutination test-CATT/T. evansi) and parasite detection tests (micro-Haematocrit Centrifugation technique, Giemsa stained blood smears, microscopic examination of lymph node aspirates and mouse inoculation). PCV was also determined. 745 dromedary camels (483 females and 262 males) were examined. Trypanosomes were detected in seven animals. 36 animals yielded CATT positive results while 709 animals were negative. All parasitologically positive animals were also CATT positive. Results showed a good correlation between CATT positive and low PCV and a higher seroprevalence in older animals. Trypanocidal drugs have not been registered in Spain and, consequently, if vigilance is not exercised the prevalence could be increased in the future.

Seroprevalence of Trypanosoma evansi in dromedaries (Camelus dromedarius) from the Canary Islands (Spain) using an antibody Ab-ELISA

After the description in Grand Canary Island of a case of dromedary trypanosomosis caused by Trypanosoma evansi in 1998, an indirect enzyme immunoassay for the detection of specific anti-T. evansi IgG (Ab-ELISA) was used to assess the seroprevalence of this disease on the Canary Islands. Seroprevalence was 9.0% in the four studied islands (Gran Canaria, Tenerife, Lanzarote and Fuerteventura), varying from 10.0 to 7.5% by island (not significantly different). Prevalence using Ab-ELISA was higher than that observed when a parasitological method (microscopic observation of blood smears) was used (1.3%).