Infectivity and virulence of Trypanosoma evansi and Trypanosoma equiperdum Venezuelan strains from three different host species.

The infectivity and virulence of seven Trypanosoma evansi and Trypanosoma equiperdum Venezuelan strains isolated from horses, donkeys and capybaras were compared in a mouse model up to 41 days, for parasitemia, animal weight, survival rates, packed cell volume, haemoglobin and erythrocyte count. Two T. equiperdum strains and three of the T. evansi strains resulted in 100% mice mortality, while the two T. evansi donkey strains exhibited lower infectivity and mortality. T. equiperdum strains had shorter pre-patent periods (4 days) than the T. evansi strains (4-12 days). In terms of pathogenicity, only the T. evansi horse strain and the two capybara strains produced a significant decrease of the packed cell volume, in haemoglobin concentration and in red blood cell count. In contrast, the T. evansi donkey strains did not show any changes in the hematological parameters. From the seven variables studied, only pre-patent period, day of maximum parasitemia, day of first parasitemia peak and number of parasitemia peaks were statistically significant. Weight decrease was only observed in mice infected with the T. evansi horse strain. T. equiperdum strains showed the highest mice lethality (7% survival by day 8 post-infection) with no change in the hematological parameters. The three T. evansi horse and capybara strains showed 80%, 87% and 97% survival rates, respectively by day 12 post-infection. However, by day 20 post-inoculation all the mice infected with the T. evansi horse strain died, while 53% and 27% capybara strains infected survived. Whereas by day 40 post-infection, 53 and 73% of the mice infected with the T. evansi donkey strains had survived. These results demonstrate striking infectivity and virulence differences between Venezuelan T. evansi and T. equiperdum strains in NMRI mice and open new possibilities to characterize inter and intra-species variations that may contribute to the pathogenicity of these two species.

Detection of Theileria equi and Babesia caballi infections in Venezuelan horses using Competitive-Inhibition ELISA and PCR.

The focus of this study was the detection of equine piroplasmosis in Distrito Capital, Miranda, Aragua, Guárico and Apure States from Venezuela, using two methods: Competitive-Inhibition ELISA and multiplex PCR and the analysis of the possible differences in occurrence in relation to the primary purpose of the horses, which is related to varied degrees of exposure to tick. Antibody levels to Babesia caballi and Theileria equi were assessed in 694 equine serum samples using Competitive-Inhibition ELISA, while PCR assays were performed in 136 horses, using two sets of oligonucleotides to establish the presence of T. equi, B. caballi or both. The overall seroprevalence of equine piroplasmosis was 50.2%, antibodies to B. caballi were found in 161 horses (23.2%), whereas 97 (14.0%) were seropositive to T. equi and 90 (13.0%) were positives to both parasites (mixed infections). PCR determinations (n=136) showed a prevalence of 66.2%, distributed in 84 (61.8% positives) for T. equi and, 6 (4.4%) were positive to both parasites. The cELISA showed higher levels of prevalence of B. caballi and mixed infections, as compared to the PCR method. This discrepancy can be explained by the different parameters that are evaluated by each technique, PCR detect the parasite itself, while cELISA detects antibodies to the parasite. By PCR, the highest prevalence was found in Apure state, where 92.3% of the samples were positive to T. equi infections. In this locality, free grazing animals are used for livestock management. This high prevalence may be linked to the tick species present in that area. More epidemiological studies will be necessary to assess the epidemiological status of equine piroplasmosis in Venezuela.

Secretome of animal trypanosomes.

Animal trypanosomosis is one of the most severe constraints to agricultural development in sub-Saharan Africa and is also an important disease of livestock in Latin America and Asia. The causative agents are various species of protozoan parasites belonging to the genus Trypanosoma, among which T. congolense and T. evansi are the major pathogenic species. The extracellular position of trypanosomes obliges us to consider both the parasite and its excreted/secreted factors in the course of the physiopathologic process. The advent of proteomics led us to propose a comparative approach of the proteome (i.e., the whole parasite content) and the secretome (i.e., naturally excreted/secreted molecules) of T. congolense and T. evansi with particular attention to common and specific molecules between strains of differing virulence and pathogenicity. The molecular identification of differentially expressed trypanosome molecules correlated with either the virulence process or the pathogenicity will provide new potential molecular targets for improved field diagnosis and chemotherapy of animal trypanosomosis.

Evaluación de la anaplasmosis en becerros mestizos holstein naturalmente infectados y desafiados con aislados homólogos y heterólogos de anaplasma marginale / Evaluation of anaplasmosis in naturally infected crossbred-holstein calves challenged with homologous and heterologous isolates of anaplasma marginale

A pesar de la características endémica de la anaplasmosis en Venezuela, son pocos los estudios que refieren a la protección cruzada entre los diferentes aislados venezolanos de anaplasma marginale. El objetivo de este trabajo consistió en evaluar el desarrollo de la enfermedad de becerros mestizos Holstein infectados naturalmente con el aislado Lara y posteriormente desafiados con aislados homólogos y heterólogos de la rickettsia, en la búsqueda de protección cruzada. Para el logro de estos objetivos, se adquirieron becerros mestizos Holstein de un semana de nacidos en un finca del estado Lara, infectados de manera natural con A. marginale, y se dividieron en tres grupos de tres animales cada uno. A los seis meses de edad fueron reinfectados con un inóculo de 5 x 10 elevado a la 8 eritrocitos infectados con A. marginale del aislado homólogo Lara (grupo I), aislados heterólogos Táchira (grupo II) y Zulia (grupo III). Desde el comienzo de los experimentos se tomaron muestras de sangre completa para evaluar parasitemia y hematocrito y se evaluaron los signos clínicos. Los tres grupos fueron diferentes en relación al período pre-patente, porcentajes de disminución de hematocrito y niveles de parasistema después del desafío. Dos de los tres animales del grupo I resultaron protegidos contra el reto homólogo, al no manifestar características compatibles con la enfermedad, mientras que los animales de los grupos II y III presentaron evidencias clínicas de anaplasmosis. El grupo inoculado con el aislado de Zulia presentó mayor severidad clínica que el grupo desafiado con el aisldo Táchira

[Prevalence of Anaplasma marginale and specific antibodies in new born calves]. / Prevalencia de Anaplasma marginale y anticuerpos específicos en becerros neonatos.

Anaplasma marginale is an intraerythrocytic rickettsia that affects the cattle and constitute a constraint for its production. The transplacental transmission of A. marginale could be of importance under field conditions, but until now no data is available to interpret its relevance in Venezuela. The goal of this work was to evaluate both the presence of A. marginale and the antibody response against the rickettsia in new born calves. Fourteen calves, one week old, were simultaneously bled for parasitological tests, packed cell volume measurement and to obtain sera for immunoenzymatic assays. All the animals showed parasitemia between seventeen and thirty days old. The antibody IgM and IgG response at this time was low. Probably, these calves acquired A. marginale infection through transplacental route and a very low level of immunity by the colostrum.

Prevalencia de Anaplasma marginale y anticuerpos específicos en becerros neonatos / Prevalence of Anaplasma marginale and specific antibodies in new born calves

Anaplasma marginale is an intraerythrocytic rickettsia that affects the cattle and constitute a constraint for its production. The transplacental transmission of A. marginale could be of importance under field conditions, but until now no data is available to interpret its relevance in Venezuela. The goal of this work was to evaluate both the presence of A. marginale and the antibody response against the rickettsia in new born calves. Fourteen calves, one week old, were simultaneously bled for parasitological tests, packed cell volume measurement and to obtain sera for immunoenzymatic assays. All the animals showed parasitemia between seventeen and thirty days old. The antibody IgM and IgG response at this time was low. Probably, these calves acquired A. marginale infection through transplacental route and a very low level of immunity by the colostrum.