Oral route of transmission: Trypanosoma evansi in a mice model experiment.

Twelve Swiss albino mice of either sex and equal body weight were randomly divided in 2 groups (I and II), consisting of 9 and 3 mice respectively and were used to conduct the study. A dose of 2.5 × 104 number of Trypanosoma evansi was instantly fed to each mouse of group I. Each mouse of group II was inoculated intraperitoneally with same dose of parasites through infected mice blood and kept separate. The tail blood of each mouse was examined daily up to 30 days post infection by examination of wet blood film and Giemsa-stained blood smears for presence of any trypanosomes. Out of 9 mice of group I those were infected orally, 3 (33.33%) mice became positive for presence of T. evansi both by examination of wet blood film and Giemsa-stained blood smears after 4, 6 and 7 days post infection. After 2 days post infection all intraperitoneally infected mice were found positive for T. evansi. Thus incubation period in orally infected mice was longer than the intraperitoneally infected mice. All the positive mice of both the groups died with high parasitaemia after 3-4 days of first appearance of parasitaemia. From the present study, it can be concluded that besides mechanical or parenteral means of transmission, T. evansi could also be transmitted through oral route. Thus zoo carnivores might be infected with T. evansi and develop disease by eating infected blood or flesh of the infected animals, as a prey and predator relationship.

Experimental studies on survivality and degenerative changes of Trypanosoma evansi after death of host.

Twenty adult Swiss albino mice, 20 rats and 10 rabbits were artificially infected with Trypanosoma evansi and killed at the peak of parasitaemia to know the period of survivality of T. evansi and degenerative changes of the parasite after death of these hosts. Examination of Giemsa stained blood smears and wet blood smears revealed the presence of parasites and live trypanosomes along with motility in the heart blood of mice and rats up to 14 h and in rabbits up to 13 h post death. Mouse inoculation test (MIT) conducted with heart blood up to 13 h post death of mice and rabbits became positive. MIT with both heart blood and portal blood of rats became positive up to 14 h post death. The liver and lung impression smears could detect the parasites up to 14 h of death of mice and rats and up to 13 h post death of rabbits whereas spleen impression smears revealed the presence of parasites up to 12 h post death of these animals. It is confirmed that T. evansi infection in animals may be diagnosed after post mortem examination of hosts by demonstration of parasites.

Seroprevalence of brucellosis in yaks (Poephagus grunniens) in India and evaluation of protective immunity to S19 vaccine.

The present study was carried out to explore the seroprevalence of brucellosis in yaks of North-Eastern hilly yak tracts of Arunachal Pradesh, India. Of 374 animals tested, 23.79, 21.11 and 18.98% were found positive for brucellosis using avidin-biotin ELISA (AB-ELISA), Rose-Bengal plate test (RBPT) and standard tube-agglutination test (STAT), respectively. The relative sensitivity and specificity for STAT were 79.77 and 100%, respectively and the same for RBPT were 88.76 and 100%, respectively in comparison to AB-ELISA. The alarming prevalence as recorded was highest among the yak cows (31.42%) followed by heifers (23.85%) and bulls (8.88%). The immune response in yaks following standard dose of calfhood vaccination with Brucella abortus strain 19 vaccine showed that protective antibody level persisted up to 210 days. This is the first report from India on prevalence of brucellosis and immunization with B abortus strain 19 vaccine in yaks. The present investigation would be a valuable guideline for future control measure and eradication programme of brucellosis in yaks.

First report of establishment of Trypanosoma evansi infection in pigeon nestlings (Columba livia).

Trypanosomosis (surra) caused by Trypanosoma evansi is quite common among horses where the parasite is endemic. In the present study, T. evansi was isolated from an infected horse and maintained by subinoculation in Swiss albino mice. At the peak of parasitemia (5 x 10(6) parasites per ml of blood), 0.25 ml of the tail blood from infected mice was inoculated intraperitoneally and subcutaneously to 2 groups of adult pigeons and 2 groups of pigeon nestlings. Four days after inoculation, the trypanosomes occurred in the peripheral circulation of pigeon nestlings, but no parasitemia was observed in adult pigeons. The body temperatures of infected nestlings increased to 104 F, whereas uninfected controls remained steady at 102 F; thus, elevated temperatures coincided with parasite presence in the peripheral circulation. A decrease in hemoglobin concentration of blood also was observed in infected nestlings. On microscopic examination, increases in length and breadth of trypomastigotes and vigorous flagellar movement of the parasites were observed. The virulence and pathogenicity of the parasites after adaptation to nestlings remained unchanged for albino mice as proved by the death of all subinoculated mice. Furthermore, polymerase chain reaction studies confirmed that the genomic DNA of trypanosomes in pigeon blood was the same as that of T. evansi. This is the first report of the establishment of T. evansi infection in pigeon nestlings.