Experimental Trypanosoma evansi infection in the goat. I. Clinical signs and clinical pathology

First molecular detection and identification of Trypanosoma evansi in goats from Cebu, Philippines using a PCR-based assay

The increasing number and severity of surra outbreaks in the Philippines led the government to consider it as the second most important disease of livestock in the country. It is one of the most economically important animal parasitic diseases and has been reported in several animal species, including water buffaloes, cattle, and horses in different regions of the Philippines. However, it has not yet been reported in Cebu, the usual gateway of livestock trade in the area that raises 6% of the 3.75 million goats in the country. In the current study, a PCR-based assay was conducted for the molecular detection and characterization of Trypanosoma evansi in goats in Cebu. A total of 251 goats were randomly sampled from four farms. DNA was extracted and ITS1-PCR was applied to detect different trypanosomes in goats. Eighty-five out of the 251 (33.9%) samples tested positive for T. evansi, two of which were also positive for T. theileri-like trypanosome. The detection rate of T. evansi was slightly higher in male goats (38.3%) than in females (32.5%), and in younger goats (34.5%) than in adults (33.5%). The findings, however, did not differ significantly to suggest any association between sex and age with T. evansi infection in goats. The detection of T. evansi and T. theileri-like trypanosome in goats was confirmed by sequence analysis of ITS1 region. To our knowledge, this is the first report on the molecular detection and identification of caprine T. evansi infection in Cebu, Philippines.

Trypanosoma evansi impacts on embryonic neural progenitor cell functions

Trypanosoma evansi appears to have a significant tropism for brain tissue in its chronic and acute phases. The most common symptoms of this brain infection are motor incoordination, meningoencephalitis, demyelination, and anemia. There have only been few studies of the effects of T. evansi infection on neuronal differentiation and brain plasticity. Here, we investigated the impact of the congenital T. evansi infection on brain development in mice. We collected telencephalon-derived neural progenitor cells (NPCs) from T. evansi uninfected and infected mice, and cultivated them into neurospheres. We found that T. evansi significantly decreased the number of cells during development of neurospheres. Analysis of neurosphere differentiation revealed that T. evansi infection significantly increased neural migration. We also observed that T. evansi promoted expression of glial fibrillary acidic protein (GFAP) in infected cells. These data suggest that congenital T. evansi infection may affect embryonic brain development.

Biocompatibility and Targeting Efficiency of Encapsulated Quinapyramine Sulfate-Loaded Chitosan-Mannitol Nanoparticles in a Rabbit Model of Surra

Quinapyramine sulfate (QS) produces trypanocidal effects against the parasite Trypanosoma evansi but is often poorly tolerated and causes serious reactions in animals. The encapsulation of QS in chitosan-mannitol to provide sustained release would improve both the therapeutic effect of QS and the quality of life of animals treated with this formulation. QS was encapsulated into a nanoformulation prepared from chitosan, tripolyphosphate, and mannitol nanomatrix (ChQS-NPs). ChQS-NPs were well ordered in shape, with nanoparticle size, as determined by transmission electron microscopy and atomic force microscopy. Our research revealed dose-dependent effects on biosafety and DNA damage in mammalian cells treated with ChQS-NPs. ChQS-NPs were absolutely risk-free at effective as well as many times higher doses against T. evansi ChQS-NPs were effective in rabbits, as they killed the parasites, relieving the animals from the clinical symptoms of the disease. The extent of this protection was similar to that observed with the conventional drug at higher dosages (5 mg QS/kg of body weight). ChQS-NPs are safe, nontoxic, and more effective than QS and offer a promising alternative to drug delivery against surra in animal models. ChQS-NPs may be useful for the treatment of surra due to reduced dosages and frequency of administration.

Comparison of infectivity and virulence of clones of Trypanosoma evansi and Ttrypanosoma equiperdum Venezuelan strains in mice

Livestock trypanosomoses, caused by three species of the Trypanozoon subgenus, Trypanosoma brucei brucei, T. evansi and T. equiperdum are widely distributed and limit animal production throughout the world. The infectivity and virulence of clones derived from Trypanosoma evansi and Trypanosoma equiperdum Venezuelan strains were compared in an in vivo mouse model. Primary infectivity and virulence determinants such as survival rates, parasitemia levels, PCV, and changes in body weight and survival rates were monitored for up to 32 days. The T. equiperdum strain was the most virulent, with 100% mortality in mice, with the highest parasitemia levels (7.0 × 10⁷ Tryps/ml) and loss of physical condition. The T. evansi strains induced 100% and 20% fatality in mice. Our results show that the homogeneous parasite populations maintain the virulent phenotype of the original T. equiperdum and T. evansi stocks. This is the first comparative study of infectivity and virulence determinants among clonal populations of T. equiperdum and T. evansi.

Effects of experimental Trypanosoma evansi infection on pregnancy in Yankasa ewes

Twenty pregnant Yankasa ewes were assigned to three groups to determine the effect of Trypanosoma evansi infection on pregnancy. Groups A and B comprising seven ewes each were infected with approximately 1.0 × 10(6) cells of T evansi per ewe through venepuncture at the second and third trimesters of pregnancy, respectively. Group C comprising six ewes served as uninfected control. There was slight pyrexia in the infected groups (groups A and B) but was absent in group C. The mean body weight, glucose concentration, and packed cell volume of ewes in group A were not significantly different from those in group C throughout the study. There was also no significant difference in mean glucose concentration between groups B and C. However, in group B, mean body weight was significantly (P < 0.05) lower compared to group C at week 2 and from week 4 post infection (pi) till the end of the study; the packed cell volume also significantly (P < 0.05) decreased but at weeks 4 and 6 pi. The mean plasma protein of ewes in group A was significantly (P < 0.05) increased compared to those of group C at weeks 7, 11 pi and thereafter till the end of the study. On the contrary, the plasma protein of ewes in group B decreased significantly (P < 0.05) compared to those in group C at weeks 2 and 6 pi. There were no reproductive losses throughout the study. This was characterized by insignificant differences in the gestation length between ewes in the infected groups (groups A and B) compared with those in group C. However, there were significant (P < 0.05) decreases in lamb birth weights of ewes in group B compared with ewes in groups A and C. Mice inoculation with blood from infected ewes postpartum was parasitemic 18 to 25 days pi, for ewes in group B, whereas none of the mice in groups A and C were parasitemic. Lambs born from the infected groups (groups A and B) were also aparasitemic for 40 days postpartum. It was therefore concluded that the T evansi isolate used caused mild trypanosomosis when infected at third trimester, whereas ewes infected at second trimester were resistant.

CpG-ODN Class C Mediated Immunostimulation in Rabbit Model of Trypanosoma evansi Infection

CpG oligodeoxynucleotides (CpG-ODN) stimulate immune cells from a wide spectrum of mammalian species. Class C CpG-ODN is relatively stable and has the combined immune effects of both A and B classes of CpG-ODN. Trypanosoma evansi produces the state of immuno-suppression in the infected hosts. The current chemotherapeutic agents against this parasite are limited in number and usually associated with severe side effects. The present work aimed to determine the immunostimulatory effects of CpG-ODN class C in T. evansi infected rabbits. Rabbits inoculated with CpG C and challenged with T. evansi resulted in delayed onset of clinical signs with reduced severity in comparison to that of T. evansi infected rabbits. The treatment also enhanced humoral immune responses. Histopathological findings in liver and spleen revealed enhancement of mononuclear cell infiltration and secondary B cell follicles. These results demonstrate that CpG-ODN class C, has immunostimulatory properties in rabbit model of trypanosomosis. The use of booster doses or sustained delivery of CpG-ODN will further elucidate the prolonged CpG-ODN generated immune responses.

Trypanosoma evansi and surra: a review and perspectives on origin, history, distribution, taxonomy, morphology, hosts, and pathogenic effects

Trypanosoma evansi, the agent of "surra," is a salivarian trypanosome, originating from Africa. It is thought to derive from Trypanosoma brucei by deletion of the maxicircle kinetoplastic DNA (genetic material required for cyclical development in tsetse flies). It is mostly mechanically transmitted by tabanids and stomoxes, initially to camels, in sub-Saharan area. The disease spread from North Africa towards the Middle East, Turkey, India, up to 53° North in Russia, across all South-East Asia, down to Indonesia and the Philippines, and it was also introduced by the conquistadores into Latin America. 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. It found a new large range of wild and domestic hosts in Latin America, including reservoirs (capybaras) and biological vectors (vampire bats). Surra is a major disease in camels, equines, and dogs, in which it can often be fatal in the absence of treatment, and exhibits nonspecific clinical signs (anaemia, loss of weight, abortion, and death), which are variable from one host and one place to another; however, its immunosuppressive effects interfering with intercurrent diseases or vaccination campaigns might be its most significant and questionable aspect.

Haematological and biochemical changes in experimental Trypanosoma evansi infection in rabbits

New Zealand white rabbits (N = 4) were challenged with the local strain of Trypanosoma evansi. Each rabbit was infected with 5 × 10(5) trypanosomes subcutaneously. The infection was characterized by intermittent pyrexia, undulating parasitaemia, anorexia and emaciation. The infected rabbits were examined daily for development of clinical signs and infection status by wet blood-films made from the ear veins. Thick and thin blood smears were also examined daily until the end of the experiment for description of blood cells. Differential leukocyte count (DLC) was also done. The parasite was observed in the blood during the acute phase only. Leukocytosis in the acute phase followed by leukopenia during the chronic phase was recognized. Haematological studies revealed reduced TEC, Hb and PCV. The main changes in the erythrocytes were macrocytes, hypochromic cells, Howell-Jolly bodies, target cells, stomatocytes and burr cells. Serum chemistry revealed hypoproteinemia, hypocholesterolaemia, hypoglycemia, hyperbilirubinemia, elevated creatinine, BUN, increased AST and ALT.

Preliminary comparison of different immune and production components in local and imported Saanen goats reared under a sub-tropical environment

Three objectives were included in this research work. The first objective compared different immune components in healthy mature males, mature females, and female kids of local and imported Saanen goats, reared under a sub-tropical environment. The significantly differing immune components were the blood monocyte percent, blood CD8 count, and the total white blood cell count. The second objective compared the performance of Saanen versus local does. The means of the milk yield and prolificacy of the imported Saanen does were significantly higher than those of the local does (p<0.05). The third objective compared the immune responses (hemagglutination-HA titers) and complement fixation (CF) titers in mature does of the two breeds to chicken red blood cells (c-RBC). The HA titers showed a significant seroconversion only in imported Saanen (p<0.05) but not in local does; however, the CF titers increased significantly at 4 weeks following priming with c-RBC in local (p<0.05) but not in the imported Saanen does. The impact of the differences in blood immune components and responses to antigens in the compared goats on protection potential against prevalent diseases in the sub-tropical zone of the eastern Mediterranean countries is discussed.

Estimating the impact of Trypanosoma evansi infection (surra) on buffalo population dynamics in southern Philippines using data from cross-sectional surveys

Despite the widespread problem with surra (Trypanosoma evansi) in livestock, there are no published studies on its impact on host populations, probably because of the large financial and time cost involved in performing longitudinal studies. During 2002-6, a cross-sectional survey for T. evansi infection involving 1732 buffaloes from 71 villages in southern Philippines was carried out. Other livestock animals (horses, cattle and goats) in every surveyed village were also tested for infection with T. evansi but domestic buffaloes were the primary survey target. Seroprevalence ranged from 6% to 21% and 13% to 100% for buffaloes in low and high risk areas, respectively. Key demographic parameters were estimated from the age structured distributions of the sampled buffalo population for each sex. All areas were dominated by females (69%) and the annual calving rate for areas of 100% and low seroprevalence was 15% and 47%, respectively. Males were removed at a relatively high annual rate of 27% in all areas. In the main reproductive years (4-10) female removal/mortality was <1% and 10% for low and high risk areas, respectively. Older females were removed/died at a rate similar to males regardless of area. In high risk areas there were consistently more 2-year than 1-year old females and the reverse was true for the low risk areas. This implies that females were imported to the high risk areas for breeding. By assuming a stable age structure and similar size populations in each area, it was estimated that 28% of female calves need to be moved from low to high risk areas to maintain the observed age structure. In high risk areas, surra imposes significant financial losses due to reduced fertility, high mortality/removal rate and the necessity to import replacement buffaloes.

Experimental Trypanosoma evansi infection in the goat. II. Pathology

Infection of male goats aged 8-10 months with 5000 or 50 000 organisms of a Mindanao strain of Trypanosoma evansi was observed over a period of 90 days. The infection induced clinical disease which was lethal, especially at the higher dose rate. Lesions were more acute in goats that received the higher dose. Gross and microscopical changes were not pathognomonic, except in the presence of demonstrable trypanosomes. At necropsy, a combination of lymphadenopathy, splenomegaly, hepatomegaly, testicular enlargement, anaemic signs and consolidation of the anterior lobes of the lungs was suggestive of surra. Testicular changes, especially aspermia, indicated probable infertility. The cytopathology of the lungs, liver, intestine, kidneys, testes, bone marrow, brain and other organs was immunological in nature, characterized by mononuclear infiltration of interstitial tissues, with minor cellular damage and the presence of trypanosomes. B- and T- cell responses were observed in the lymphatic system, but the findings indicated immunosuppression in the lymph nodes, spleen and bone marrow during the third month after infection. Exudative inflammatory changes were mild. It is suggested that the cytopathology of most haemophilic trypanosomal infections is predominantly an immunological process.