Serum proteins in guinea-pigs and horses infected with Trypanosoma evansi (Steel, 1885)

The serum protein pattern in guinea-pigs infected with T. evansi was analysed and compared with those found in horses with either a natural or experimental infection. In both species, a highly significant decrease in albumin levels and an increase in gamma-globulins were seen, leading to a very low albumin/globulin ratio. No significant differences in total protein levels between healthy and infected animals were registered. Likewise, alpha-globulins were not significantly affected. A decrease in beta-globulins was observed in one horse and in guinea-pigs with experimental infection, while in horses with natural infections this decrease was not constant. The serum protein patterns in guinea-pigs infected with T. evansi appeared similar to those occurring in horses infected with this parasite. Guinea-pigs, therefore may be useful laboratory models for the study of equine trypanosomosis caused by T. evansi.     

Surveys in Papua New Guinea to detect the presence of Trypanosoma evansi infection

OBJECTIVE: To confirm serological evidence that Trypanosoma evansi is present in Papua New Guinea. DESIGN: Three surveys were undertaken in PNG during 1997/1998. Animals were selected for sampling on the basis of convenience. Samples of blood were examined for the presence of T evansi by the haematocrit centrifugation technique (HCT) and mouse inoculation test (MI). Sera were tested in the field using the card agglutination test for trypanosomiasis/T evansi (CATT). Bovine sera were tested at James Cook University using an antibody-detection ELISA (Ab-ELISA). Results from testing bovine sera with the Ab-ELISA and sera from wallabies with the CATT were analysed using FreeCalc to determine the probability that animals in these populations were infected with T evansi. RESULTS: A total of 545 serum samples were collected, during the three surveys of which 39 cattle, two pig and three agile wallaby samples were positive with the CATT. All bovine sera collected were negative when tested with an Ab-ELISA. T evansi was not isolated using the HCT or the MI from any of these animals. CONCLUSION: Based on the Ab-ELISA results it was concluded that T evansi infection was not present in cattle in villages around Balimo at a minimum expected prevalence of 10% (P < 0.05) and, based on the CATT results, that infection was not present in wallabies on the Bula plain at a minimum expected prevalence of 10% (P < 0.1). These results indicate that it is unlikely that T evansi is endemic in PNG.     

The susceptibility of two species of wallaby to infection with Trypanosoma evansi

OBJECTIVE: To determine the susceptibility of the agile wallaby (Macropus agilis) and the dusky pademelon (Thylogale brunil) to infection with Trypanosoma evansi. METHOD: Two agile wallabies and three dusky pademelons were experimentally infected with between 5 x 10(4) and 10 x 10(4) T evansi from a cryopreserved stabilate isolated from an indonesian buffalo. Animals were observed twice daily for clinical signs and blood was collected every 3 days to determine parasitaemia. Necropsy was conducted on animals that died or were euthanised when in extremis and representative tissue sections examined. RESULTS: All wallabies developed a high parasitaemia by 6 days after infection, which persisted until death or euthanasia in extremis, between days 8 and 61. Clinical signs included anorexia, weakness and ataxia. Anaemia occurred in one wallaby that survived for 61 days. Gross pathological changes varied between animals. They included pericarditis, serous atrophy of fat, splenomegaly, ulcerative gastritis and enteritis. Histological changes were characterised by a mononuclear cell infiltration of the connective tissue of most organs with little cellular destruction. Striking lesions were seen in the choroid, heart, stomach and small intestine. CONCLUSION: Agile wallabies and pademelons are highly susceptible to infection with T evansi. Wallabies, therefore, have the potential to spread T evansi within New Guinea and Australia if infection is introduced. Mortality is likely to be high thereby acting as an indicator of recent introduction. Histological changes seen in wallabies infected with T evansi are diagnostic for infections occurring in Australia and Papua New Guinea.     

Direct and sensitive detection of Trypanosoma evansi by polymerase chain reaction.

The mechanically transmitted haemoflagellate, Trypanosoma evansi causes 'surra', a wasting disease of domestic animals and is highly endemic in distribution in Southeast Asia. The detection of T. evansi is important for improving the epizootiological and animal health status of the region. The specificity and sensitivity of polymerase chain reaction (PCR) using oligonucleotide primers constructed from T. evansi repetitive DNA sequences were studied in the present investigation. Using the assay, it was possible to amplify template DNA of T. evansi derived from buffaloes, camels and horses to a threshold sensitivity level of 0.5 pg and to detect DNA from as few as five organisms in 10 microliters crude blood samples. Following experimental infection of calves with 5 x 10(5) T. evansi, positive signals could be observed as early as 12 h post-infection. DNAs from two common haemoflagellates of cattle, Babesia bigemina and Theileria annulata were not amplified with the primers.     

泰氏锥虫抗原制备及实验室诊断研究

应用体外培养的泰氏锥虫制备可溶性抗原Ⅰ、抗原Ⅱ和代谢抗原.经测定,其蛋白含量每毫升分别为6.5mg、7.4mg和7.1mg.薄层等电聚焦电泳测定结果表明,抗原Ⅰ出现22条区带,抗原Ⅱ21条区带,代谢抗原28条区带,对照的伊氏锥虫琼脂免疫扩散抗原14条区带.经分析,泰氏锥虫抗原和伊氏锥虫抗原有4条区带在同一迁移率上.琼脂免疫扩散反应中,3种泰氏锥虫抗原均与相应免疫兔血清发生沉淀反应,抗原Ⅰ出现1条致密沉淀线,抗原Ⅱ和代谢抗原出现2～3条沉淀线,抗原效价为1:4～16.免疫电泳显示了类似的结果,抗原Ⅰ与免疫兔血清出现1条弧形沉淀线,抗原Ⅱ和代谢抗原与免疫兔血清出现了3条弧形沉淀线.间接血凝试验结果表明,泰氏锥虫自然感染牛血清效价为1:20～40,免疫兔血清为1:1280～5120.所制泰氏锥虫抗原对伊氏锥虫和媾疫锥虫血清也能很好地发生交叉反应,3份伊氏锥虫病马血清和3份伊氏锥虫人工感染兔血清血凝效价分别为1:10～40和1:8～1024;5份媾疫马血清有4份血凝效价为1:20～320.4份环形泰勒虫病牛血清均为阴性.     

Epidemiological study of the cystic echinococcosis in Morocco

The objectives of this epidemiological study on cystic echinococcosis (CE) in Morocco (2001-2004) were to update the prevalence of CE in different animal species living in the most important areas of the country and to collect protoscoleces and germinal layers for genetic research purposes. The post mortem inspection concerned 2948 sheep, 2337 goats, 618 cattle, 482 camels and 455 equines (325 horses, 60 mules and 70 donkeys) in five different regions: the Rif (Mediterranean coast and high mountains of the Rif), the Loukkos (Atlantic northwest plain), the center (Rabat and Casablanca regions), the Middle Atlas mountains and the south (arid and semi desert areas). The global CE infection prevalence rates obtained were 22.98% in cattle, 10.58% in sheep, 12.03% in camels, 17.80% in equines and 1.88% in goats. The infection rates were especially high in the Middle Atlas in cattle (48.72%) and in the Loukkos in cattle and sheep (37.61 and 31.65%, respectively). The majority of infected cattle (49.6%) and sheep (52.1%) had hydatid cysts in both liver and lungs. Except for cattle, the liver was more infected than lungs in all the other animal species. Animals more than 5 years old were the most infected in all species. The mean CE infection rates of these animals were about 56% in cattle, 40% in sheep, 20% in camels, 17.80% in equines and 7% in goats. These rates were much higher in the Loukkos (85% of cattle and 59% of sheep) and in the Middle Atlas (68% of cattle and 45% of sheep) than in the other regions. Results showed that Echinococcus granulosus is in an endemic steady state with no evidence of protective immunity in the intermediate hosts. The mean numbers of infections per year are 0.099 for cattle, 0.063 for sheep, 0.03 for camels and 0.010 for goats.     

Enzootiology of Trypanosoma evansi in Pantanal, Brazil

In order to better understand the enzootiology of trypanosomiasis caused by Trypanosoma evansi in the Brazilian Pantanal we examined domestic and wild mammals by microhematocrit centrifuge technique (MHCT), immunofluorescence antibody test (IFAT) and polymerase chain reaction (PCR). T. evansi infection was detected in all species sampled with exception of the sheep and the feral pig. High parasitemias were observed in capybaras (5/24), coatis (18/115), horses (31/321) and dogs (3/112). Among these species, only the capybaras did not develop anemia. Low parasitemias, only detected by PCR, were found in buffaloes (18/43), bovines (29/331), marsupials (1/4), small rodents (14/67), bats (7/18), and one armadillo (1/8). The highest prevalence of T. evansi infection was recorded in horses (73%), although no neurological signs in infected horses were observed. Diagnosis through standard parasitological tests and IFAT should be used with caution since they may overlook comprovedly infected horses. The relationship between ranch management and T. evansi infection in horse was investigated. The importance of other transmission mechanisms apart from the tabanids and reservoir hosts are discussed.     

Prevalence of Trypanosoma evansi in horses in Israel evaluated by serology and reverse dot blot

Trypanosoma evansi is the cause of surra in horses, camels and other domestic animals. Following the first outbreak of surra in horses and camels in Israel in 2006, a survey of the prevalence of the parasite in the Israeli horse population was conducted using serology, PCR followed by the reverse dot blot (RDB) technique and blood smear microscopy. In total, 614 horses from 7 regions were sampled. The CATT/T. evansi kit was used for serology for all the horses. Horses from the Arava and Dead Sea region, where the first outbreak occurred, were sampled again one year later and both samples were subjected to serology and the RDB technique. The country wide seroprevalence was 4.6% (28/614). The seroprevalence in the Arava and Dead Sea region was 6.5% (9/139) in the first sampling compared with 4.1% (5/122) in the second, whereas the prevalence of RDB-positivity was 18.7% (26/139) in the first sampling and only 0.8% (1/122) in the second. All horses were asymptomatic except for one horse from the Arava and Dead Sea region that demonstrated clinical signs of surra combined with positive serology and RDB. The results of this study indicated that surra is prevalent in most regions of the country and thus should be considered an important differential diagnosis in horses and other domestic animals in Israel with chronic weight loss, edema or neurological signs.     

Longitudinal study of an outbreak of Trypanosoma evansi infection in equids and dromedary camels in Israel

An outbreak of trypanosomoasis caused by Trypanosoma evansi involving horses, camels and donkeys occurred in a farm in Israel. A longitudinal study of two outbreak phases was conducted which included clinical monitoring, blood smears, packed cell volume (PCV), serology and polymerase chain reaction (PCR) followed by reverse dot blot (RDB) for the molecular detection of infection. This was the first reported T. evansi outbreak in domestic animals in Israel. Most of the camels on the farm (8/10; 80%) were diagnosed with T. evansi infection whereas infection was less prevalent in the horses (3/7; 43%) and donkeys (6/13; 46%). Clinical disease was evident in 4 camels and 1 horse exhibiting characteristic clinical signs, anemia and parasitemia detected on blood smears and by positive RDB. Six other animals were diagnosed as asymptomatic latent carriers by positive RDB and 6 additional animals were only seropositive and were considered suspected carriers. A significant difference was found in the mean PCV between symptomatic and latent carriers with severe anemia observed only in the symptomatic animals. An anaphylactic-like reaction, fatal in one case, was observed in 2 camels diagnosed with severe trypanosome parasitemia immediately following treatment with melarsenoxide cysteamine. Furthermore, recurrence of infection was documented in one camel 4 months post treatment.     

Trypanosomiasis in Indonesia. A review of research, 1900-1983

This review describes research conducted from 1900-1983 on trypanosomiasis due to Trypanosoma evansi in Indonesia. Clinical signs and post-mortem findings in horses, cattle, buffaloes, pigs and dogs, experimental transmission tests to establish possible surra vectors in Indonesia, and research on chemotherapy and chemoprophylaxis are discussed.     

Microsatellite typing and population structuring of Trypanosoma evansi in Mindanao, Philippines

Trypanosoma evansi, a blood-borne protozoan parasite with an extensive geographical range is the causative agent of the livestock disease known as surra. A total of 140 out of 179 T. evansi isolates collected between 2006 and 2007 from 44 villages (comprising of 16 reported surra outbreaks) in 3 provinces (Agusan del Sur (ADS), Surigao del Sur (SDS) and Agusan del Norte (ADN)) in Mindanao, Philippines were each successfully genotyped using a suite of 7 polymorphic microsatellites. The study identified 16 multi locus genotypes (MLG) within the T. evansi isolates and evidence of the spread of surra outbreaks from one village to another, most likely due to the movement of infected animals. Genotyping provided evidence of population sub-structuring with 3 populations (I, II and III (only 1 isolate)) identified. The most abundant population was II, which was the predominant population in ADS and SDS (p=0.022). In addition, buffalo mortality was statistically higher in outbreak areas associated with isolates from population I (13.6%) than with isolates from population II (6.9%) (p=0.047). The present study has highlighted the utility of microsatellite loci to improve understanding of the epidemiology of T. evansi and in tracking surra outbreaks.     

Isoenzyme analysis of stocks of trypanosomes isolated from cattle in Indonesia

Three trypanosome stocks isolated from cattle in Indonesia were shown to differ markedly from an Indonesian stock of Trypanosoma evansi on the basis of the isoenzyme banding patterns of 12 soluble enzymes. The results obtained for these stocks were not consistent with those reported for typical forms of T evansi but were very similar to enzyme patterns obtained for rodent adapted stocks of T vivax.     

Prevalence and risk factors associated with Cryptosporidium spp. infection in young domestic livestock in India

A total of 938 faecal samples (461 cattle calves, 264 buffalo calves, 55 lambs, 116 kids and 42 piglets) from different livestock farms and individual small holdings in six targeted states of India were collected and screened by modified Ziehl–Neelsen staining technique to determine the prevalence of Cryptosporidium spp. and its association with age, sex, season and faecal consistency in domesticated animals. Overall, 16.2 % of the animals were positive for Cryptosporidium infection with prevalence of 16.3, 24.2, 1.8, 3.5 and 19.1 % in cattle calves, buffalo calves, lambs, kids and piglets, respectively. The prevalence of infection was significantly higher (p?<?0.05) in bovines (19.3 % cattle and 33.7 % buffalo) below 1 month of age than in animals between 1 and 3 months of age. But in piglets, it was higher in the age group of 1 to 3 months (22.6 %) than in younger animals (9.1 %). Also, higher prevalence (p?>?0.05) was recorded in females than in males. Seasons had a significant effect (p?<?0.05) on the prevalence of infection in large ruminants, with the highest prevalence in monsoon (cattle 28.8 % and buffalo 36.6 %) followed by pre-monsoon and post-monsoon season. However, in case of sheep and goats, the prevalence was higher (p?>?0.05) in post-monsoon than in monsoon season. A high degree of association was noticed between Cryptosporidium infection and diarrhoea in ruminants screened during the present study. But, in case of pigs, the prevalence was higher in non-diarrhoeic than in diarrhoeic animals. Genotyping of Cryptosporidium spp. based on nested PCR amplification of partial 18S rRNA and its subsequent digestion with SspI, VspI and MboII restriction enzymes revealed prevalence of Cryptosporidium parvum in representative number of positive samples of cattle, buffalo and goats.     

Cross-sectional study on prevalence of Trypanosoma evansi infection in domestic ruminants in an endemic area of the Canary Islands (Spain)

Trypanosoma evansi is the most widely spread of the pathogenic African trypanosomes of animals. The disease (surra) was first diagnosed in the Canary Islands in a dromedary camel in 1997; thus, a control plan was implemented achieving the eventual eradication of T. evansi from most of the infected areas in the Archipelago. However, a little area remains still infected despite the use of the same control measures. To evaluate possible reservoirs in the area a representative sample of domestic ruminants was examined by serological, parasitological and molecular tests. Of a total of 1228 ruminants assessed, 61 (5%) were serologically positive (7 cattle, 21 goats, 33 sheep), but T. evansi could be demonstrated in none of them. According to FreeCalc assessment, cattle and goat populations would be free from disease; however, the results from sheep are not adequate to conclude that the population would be free from disease. As a conclusion, surveillance must be exercised on ruminant farms in the surroundings of the infected area in order to evaluate the possible extension of the disease and their potential role as reservoirs of T. evansi.     

An investigation of 11 outbreaks of foot-and-mouth disease in villages in northern Thailand

The results of investigations of 11 outbreaks of foot-and-mouth disease in villages in northern Thailand are described. The causative virus was Asia in one in seven outbreaks, Type O in two outbreaks and unknown in two outbreaks. The most probable sources of the outbreaks were co-mingling of cattle and/or buffalo with livestock from an infected neighbouring village (four) and recent introductions of infected cattle from a public livestock market (two) while the probable source could not be determined in five outbreaks. Attack rates in cattle and buffalo ranged from 0.28% to 50.9% but no pigs became sick during any of the outbreaks. Most outbreaks lasted 4 weeks or less. Adult cattle and buffalo were at higher risk of becoming a case when compared with work cattle. Beef cattle were at higher risk than buffalo and adult cattle and buffalo were at higher risk than calves less than 1 year of age. There was significant clustering of cases within households. Serological investigations indicated that many unaffected animals were probably not exposed to virus during the outbreaks. We concluded that close contact between animals was the main method of spread and that differences in attack rates between animal classes reflected differences in animal management. We further concluded that simple quarantine of early cases during outbreaks is likely to be effective in reducing spread within and between villages.     

Prevalence and clinical impact of Toxocara vitulorum in cattle and buffalo calves in northern Lao PDR

This study was completed to determine the prevalence and distribution of Toxocara vitulorum infection in cattle and buffalo calves and investigate its clinical impact in northern Lao PDR (Peoples Democratic Republic). The results aim to assist decisions on disease control measures that can contribute to increasing cattle and buffalo productivity within smallholder farming systems in tropical areas. A prevalence survey for T. vitulorum in buffalo and cattle calves aged <3 months was conducted between September 2009 and June 2010 in five provinces of northern Lao PDR using a two-stage sampling technique to select 69 villages and 899 calves, with faecal samples collected and examined for T. vitulorum eggs at a local laboratory. At the time of sampling, data on calf morbidity and anthelmintic treatment was also collected. Factors potentially associated with infection and severity of infection were analyzed at univariable and multivariable levels, using T. vitulorum status (positive/negative) and on the positive calves only, faecal egg count levels as outcome variables. The estimated prevalence of T. vitulorum in northern Lao was 22.6 % (95 % confidence interval [CI], 0.17–0.28), and 76.8 % of villages had at least one positive calf. Province was the only significant (p?<?0.05) variable investigated associated with calf infection status. Species (buffalo) was the only variable significantly (p?<?0.05) associated with higher egg per gram of faeces levels among infected calves. Prevalence in calves aged 1–21 days, the reported prepatent period, was 17.5 % (CI 0.11–0.24). Treatment levels were very low (8.2 %) and if treatment occurred it was mostly unsuccessful. The high and wide spread infection of T. vitulorum in cattle and buffalo calves identified in this survey is likely to result in suboptimal cattle and buffalo productivity. Improved management of T. vitulorum infection in cattle and buffalo calves in northern Lao PDR is indicated to reduce potential negative production impacts and enable more efficient development of large ruminant livestock industry as a pathway from rural poverty for smallholder farmers in northern Lao PDR. In addition to quantifying this disease problem in calves, the conduct of this applied participatory research study provided an important opportunity to improve animal health services by increasing the parasite, large ruminant handling and research knowledge and capacity of government animal health staff and farmers.     

The development and validation of an antibody-ELISA to detect Trypanosoma evansi infection in cattle in Australia and Papua New Guinea

Trypanosoma evansi is exotic to Australia and Papua New Guinea (PNG). However, it might have been introduced to Papua (Indonesia); thus, there is a risk of it entering PNG and thence Australia. Because of logistical difficulties in PNG and northern Australia, surveillance for T. evansi must rely on serological tests. The accuracy of an Ab-ELISA using a detergent extract of T. evansi and three antigen fractions purified from the detergent extract using stepwise precipitation with saturated ammonium sulphate (AS) were compared. The ELISA using the AS 40-50% fraction had greater discriminatory power compared to the ELISA using the other antigen fractions. This ELISA then was compared with two commercial tests: the Card Agglutination Test for trypanosomiasis/T. evansi (CATT) and Suratex. CATT/T. evansi at 1/4 serum dilution has higher sensitivity and the ELISA has higher specificity. There is no likely benefit in combining antibody detection tests to improve the accuracy of diagnosis. Furthermore, the combination of Suratex (which was independent of the antibody tests) with the CATT or the ELISA did not improve the sensitivity. None of the tests was sufficiently sensitive to be used confidently to determine freedom from infection in animals imported into Australia from countries where T. evansi infection is endemic.     

Haemoparasite prevalence and Theileria parva strain diversity in Cape buffalo (Syncerus caffer) in Uganda

Cape buffalo (Syncerus caffer) are considered to be an important reservoir for various tick-borne haemoparasites of veterinary importance. In this study we have compared the haemoparasite carrier prevalence in buffalo from four geographically isolated national parks in Uganda [Lake Mburo National Park (LMNP), Queen Elizabeth National Park (QENP), Murchison Falls National Park (MFNP) and Kidepo Valley National Park (KVNP)]. Differences were seen in haemoparasite prevalence in buffalo from the four national parks. All the buffalo sampled in LMNP were carriers of Theileria parva however, buffalo from MFNP and KVNP, which are both located in the north of Uganda, were negative for T. parva. Interestingly, 95% of buffalo in the northern part of QENP were T. parva positive, however all buffalo sampled in the south of the park were negative. A high multiplicity of infection was recorded in all the buffalo found to be carrying T. parva, with evidence of at least nine parasite genotypes in some animals. Most of the buffalo sampled in all four national parks were carriers of T. mutans and T. velifera, however none were carriers of T. taurotragi, Babesia bovis, Babesia bigemina, Ehrlichia bovis or Ehrlichia ruminantium. All the buffalo sampled from LMNP were positive for T. buffeli and T. sp. (buffalo) however, buffalo from the parks in the north of the country (KVNP and MFNP) were negative for these haemoparasites. Anaplasma centrale and Anaplasma marginale were circulating in buffalo from all four national parks. T. parva gene pools from two geographically separated populations of buffalo in two of the national parks in Uganda (LMNP and QENP) were compared. The T. parva populations in the two national parks were distinct, indicating that there was limited gene flow between the populations. The results presented highlight the complexity of tick-borne pathogen infections in buffalo and the significant role that buffalo may play as reservoir hosts for veterinary haemoparasites that have the potential to cause severe disease in domestic cattle.     

Trypanosoma evansi infection in bovine and buffalo calves in Indonesia.

Fifteen bovine and 11 buffalo calves born on different farms in a Trypanosoma evansi-endemic area of West Java were monitored for the presence of T. evansi and T. evansi antibody at monthly intervals until they were 12 months of age. Fifty percent of the bovine and 83% of the buffalo calves sampled in the first month of life were antibody positive. This antibody was considered to be of colostral origin. Antibody developing later in life persisted for up to 12 months and was considered to have arisen in response to T. evansi infection. No protective function could be ascribed to the colostral antibody.     

Influence of Trypanosoma evansi infection on milk yield of dairy cattle in northeast Thailand.

Effect of subclinical Trypanosoma evansi infection on the milk yield of newly introduced Holstein Friesian dairy cattle were investigated. Five hundred pregnant heifers were introduced in Loei Province, northeast Thailand and a total of 168 blood samples were collected at 20 farms during 6 visits over 2 years. Trypanosomes were found in cattle in June and November 1996, after which the parasite was rarely seen. On the other hand, the infection prevalences by antigen-detection ELISA (Ag-ELISA) were around 40% from the first sampling through October 1997; then, antigenemic cattle decreased to 20% by June 1998. Milk yields of the cattle with detectable parasitaemia in June and November 1996 were significantly lower than those of the non-infected cattle by Student's t-test. Similarly, the milk yields of Ag-ELISA positive cattle were lower than those of negative cattle at every sampling and significant differences were observed during the first year and in February, 1998 (tested by 2-way ANOVA; T. evansi status and herd as factors). This study suggested that subclinical trypanosomosis caused decrease in milk yield of newly introduced dairy.