Seroprevalence of Trichinella in slaughter pigs in Kathmandu Valley, Nepal.

The aim of the present study was to determine the Trichinella seroprevalence in slaughter pigs in Kathmandu Valley, Nepal. Serum samples were obtained from 400 pigs at 4 major slaughterhouses and tested for Trichinella antibodies by ELISA using larval excretory-secretory (E/S) antigen. Four were positive and one was equivocal, giving a Trichinella seroprevalence of 1% (95% CI: 0.27 - 2.54). On titration, all positive and equivocal samples had titers greater than 1:80. Upon re-examination the equivocal sample failed to give a positive ELISA result. The pigs were from four major areas of Nepal, Kathmandu Valley, eastern Nepal, Terai and adjoining areas of the valley. Positive results were found from only Kathmandu Valley and adjoining areas. There was no significant difference in the prevalence between areas (p = 0.43). All four positive samples were from indoor managed pigs. The Trichinella seroprevalence determined in this study deserves a direct demonstration of the parasites for proof of the presence of Trichinella in Nepal and to discover the species and infection sources.

Proposals for epidemiological surveys of helminthoses aimed at the improvement of livestock production in the tropics.

As the major contagious epidemics in the tropics are today more or less under control, the most important diseases of livestock are due to parasitic infections. Precise knowledge concerning the biology of parasites and their seasonality is a prerequisite for any control strategy. Therefore, epidemiological investigations into the effect of helminths on ruminant livestock production must include I. A vertical section through the age dependent helminthic burden of a representative number of animals of a given population, i.e. the sampling of faeces at regular intervals during the first 18 months of life. II. Investigations into the horizontal development of the helminthic situation, whether soil-transmitted and/or vector-transmitted. a. The seasonal fluctuation of egg excretion from gastrointestinal nematodes. b. The seasonal incidence of nematode larvae on pastures. c. The seasonal survival time of nematodes larvae on pastures. III. The seasonal fluctuation of vector snails and their incidence of infection with trematode larvae. For the economic evaluation of control measures it is necessary that the following parameters should be recorded: The age dependent mortality rate, the development of the average body weight, the birth/slaughter weight, the age at first calving and the calving intervals.

Production of interleukin 2 and expression of interleukin 2 receptors by pony peripheral blood lymphocytes after stimulation with a soluble fraction of Trypanosoma evansi.

Pony peripheral blood lymphocytes (PBL) were stimulated with a soluble fraction of Trypanosoma (T.) evansi (SF). As determined by 3H-thymidine incorporation, the cells underwent a proliferative response and were able to: a) produce a factor having the biological activities of interleukin 2 (IL-2) since their supernatants could support the in vitro growth of pony PBL stimulated with concanavalin A (Con A-blasts); b) undergo a further proliferative response when incubated in short term cultures with SF, human recombinant IL-2 (hrIL-2), or both c) bind specifically radiolabelled hrIL-2 (125I-hrIL-2). The date described here indicate that a soluble fraction of T. evansi stimulated pony PBL which subsequently produced IL-2 and expressed IL-2 receptors (IL-2R).

Application of luminol-dependent chemiluminescence to assay opsonizing antibodies to procyclic forms of Trypanosoma congolense in the sera of dogs experimentally infected with heterologous stocks.

Luminol-dependent chemiluminescence (LCL) responses of dog granulocytes were used to assay opsonizing antibodies to procyclic culture forms of T. congolense. A high degree of sensitivity was demonstrated and LCL levels were high, when the phagocytic cells were incubated with the sera of infected dogs even at dilutions as high as 1:400 as compared to pre-infection or negative sera. The levels of opsonizing antibodies were elevated in all the dogs throughout the time of observation. The technique was sensitive, could be automated and, therefore, allows a rapid evaluation of large numbers of serum samples for Trypanosoma specific antibodies.

Production and consumption of T cell growth factor by peripheral blood lymphocytes of cattle infected with Taenia saginata.

Calves were infected with 25,000 or 50,000 viable eggs of Taenia saginata. Larval numbers ranged between 2077 and 6005. During infection the animals developed leucocytosis, which was mainly due to lymphocytosis. An apparently positive correlation was observed between the lymphocytosis and the in vitro proliferative response of the lymphocytes to antigen prepared from proglottids. Maximal in vitro blast transformation of the cells stimulated with antigen occurred on Days 12 and 32 post-infection (p.i.). Specific antibodies to T. saginata were demonstrated on Day 14 p.i. At that time, the proliferative response of the cells paralleled the formation of specific antibodies, particularly of the IgG class. The stimulated cells produced a lymphokine showing interleukin 2 (IL 2)-like activity, since the addition of supernatant of such cells to IL 2-dependent concanavalin A (Con A)-blast cells supported the in vitro growth of the cells. In addition, peripheral blood lymphocytes (PBL) specific for T. saginata could be maintained in long-term cultures when they were cultured in medium containing supernatants of MLA-144 cell lines. The data presented in this study indicate that cells specific for T. saginata produced and consumed T cell growth factor (TCGF).

Metaphylactic deworming program for buffalo calves (Bubalis bubalis) in North-East Thailand.

One hundred newborn swamp buffalo calves (Bubalis bubalis) from three villages in North-East Thailand were divided equally into treatment and control groups. Treated calves received two doses of a piperazine/thiabendazole mixture (196.6 and 50 mg/kg bodyweight respectively) at three, and again at ten weeks of age. Control calves received placebo treatments at the same times. Egg excretion rates for the roundworms Strongyloides papillosus and Toxocara vitulorum were recorded as high as 85% and 58% respectively during the first three months of life. During the trial period, four calves in the treated group died and one was treated for coccidiosis, compared to seven deaths and nine additional anthelmintic treatments required in the control group. All calves that either died or required additional anthelmintic treatment showed signs of severe enteritis, anorexia and emaciation that was attributed to parasitic infestation. Calves receiving emergency anthelmintic treatment all recovered uneventfully. All except four of the calves that died or became sick did so between 25 and 40 days post partum, with the remainder developing clinical signs of parasitosis before day 50. There was no difference in weight gains between treated and untreated calves over the trial period (16 weeks). Thus, the advantage of anthelmintic treatments as described at three and ten weeks of age in buffalo calves under village conditions was seen as a reduction in the combined morbidity/mortality rate from 32% to 10% (P less than 0.05). From the pattern of infection observed in this study it is suggested that further gains could be made by giving the second treatment at six (instead of ten) weeks of age, and by increasing the dosage of anthelmintic used.

Studies on the sequence of variable antigen types in ponies infected with a clone of Trypanosoma evansi.

The sequential appearance of variable antigen types (VATs) of a clone of Trypanosoma evansi was studied in four ponies. Using luminol-dependent chemiluminescence, VAT populations which had been isolated from parasitemic peaks of single ponies, were tested for specificity with serum samples collected from other ponies. When antibody activity was demonstrated in a combination of trypanosomes and serum, it was concluded that a major VAT appeared in common. In the serum of all animals antibody activity was demonstrated to all VAT populations isolated from the other ponies during the first 4 weeks of infection, indicating that up to this moment in all four animals the same major VATs developed. The sequence of major VATs was very similar in all ponies. Several parasitemic waves consisted of more than one major VAT, and in another pony a certain major VAT developed either in the same or in a neighbouring wave of the parasitemia.

West African dogs as a model for research on trypanotolerance.

Autochthonous dogs from Liberia/West Africa were reared trypanosome-free and brought to West Berlin/germany. Together with Beagle dogs they were infected cyclically by tsetseflies with Trypanosoma congolense. While the European dogs died soon of the trypanosomal infection, the African dogs developed milder parasitaemias and remained clinically unaffected. The authors' opinion is, that this dog model could make a contribution to research on trypanotolerance.

Antigenic variation of Trypanosoma evansi in rabbits.

In order to study the occurrence and sequential appearance of antigenic variation during the course of T. evansi-infection, rabbits were infected with a clone prepared from T. evansi, Java/55/PTV/1 (stock 1, clone 5). During the course of infection, trypanosome-populations were isolated from the cerebrospinal fluid and from each parasitaemia peak. Specific antisera against the clone, 6 parasitaemia-populations and two different liquor-populations (all isolated from 1 rabbit), were produced in rabbits. These antisera were used for the characterization and comparison of trypanosome populations with each other by means of immunolysis as well as neutralisation-infectivity-(NIF)-test. It was found that in all infected rabbits, the first parasitaemia contained trypanosomes, which were almost identical to those present in the clone. However, the clone contained already minor variant antigenic types ("minor-VATs"). All trypanosome-populations isolated from rabbits were heterogeneous. Heterogeneity was more pronounced in the later phases of the infection. After each fluctuating parasitaemia new dominant variants ("major VAT") were expressed. The sequential appearance of antigenic variation was similar among all infected animals. The effectivity of immunolysis was checked by the NIF-test. As it was expected, complete lysis of all trypanosomes of a population was not achieved, because some "minor VATs" could escape the influence of the antiserum. By this way, they formed the basis of new "major VATs" which dominated in the next fluctuating parasitaemia.

Trypanosoma brucei brucei infection in goats. Response of peripheral blood lymphocytes to mitogen stimulation.

The in vitro proliferative response of peripheral blood lymphocytes from Trypanosoma b. brucei infected goats to mitogens was studied during the course of infection. An inverse correlation was observed between the number of lymphocytes and their capacity to respond to concanavalin A, phytohemagglutinin and pokeweed mitogen. Lymphocyte responsiveness to mitogens was reduced during a period of increased lymphocyte counts. During this period of time only few trypanosomes were detectable in the peripheral blood. Later in the infection, when lymphocytes decreased, mitogen responsiveness and parasitemia increased.

Immunological aspects of Theileria annulata infection calves. 2. Production of macrophage migration inhibition factor (MIF) by sensitized lymphocytes from Theileria annulata-infected calves.

Peripheral blood lymphocytes (PBLs) from calves infected experimentally with a stabilate of Theileria annulate, produced a factor which inhibited the migration of macrophages. This was first demonstrated against schizont antigen in some animals on day 8 post infection while in the others on day 12. The highest activity of the macrophage migration inhibition factor (MIF) was recorded on day 12 in some of the infected animals and on day 16 in the others, whereas on day 30 or more MIF was demonstrable. The MIF was also demonstrated against piroplasm antigen. 64 days after the first infection, the recovered calves were challenged with the homologous strain. It was found that PBLs from all challenged calves were able to produce MIF against both, schizont and piroplasm antigen. These results indicate occurrence of sensitized lymphocytes as effector cells of cell-mediated immunity to T. annulata infection.