Effect of chronic fenvalerate (synthetic pyrethroid) intoxication on the immune response of goats to Brucella abortus strain 19 vaccine.

Fenvalerate, a widely used pesticide, was administered orally to goats at a dose rate of 15 mg/kg body weight, daily for 270 days. After 90 days of dosing, the animals, together with appropriate controls, were vaccinated with Brucella abortus strain 19. The fenvalerate reduced both the humoral and cell-mediated immune responses, as assessed by the standard tube agglutination test and delayed hypersensitivity test, respectively.

Immunosuppression due to chronic Lantana camara, L. toxicity in sheep.

Five sheep were intoxicated with powdered L. camara, leaves at the rate of 200 mg/kg body weight daily for 110 days and another group of four sheep were drenched with distilled water daily for equal number of days which acted as control. The cell mediated immunity of intoxicated and control sheep was assessed with the help of 2,4-dinitrofluorobenzene skin sensitivity test and graft-versus-host reaction and the antibody forming potential of both the groups of animals was measured by haemagglutination against chicken red blood cells antigen. In addition, the phagocytic activity of splenic reticulo-endothelial cells was analysed by nitro blue tetrazolium test. The results indicated significant reduction of both cellular and humoral immunity due to L. camara toxicity. The non-specific phagocytic activity of splenic reticulo-endothelial cells also showed significant reduction due to L. camara, L. intoxication. The present communication constitutes the first report of in vivo immunosuppression due to chronic lantana poisoning in sheep.

Suppression of cell-mediated immunity by purified aflatoxin B1 in broiler chicks.

The effect of purified aflatoxin B1 on cell-mediated immunity (CMI) in broiler chicks was assessed using doses of 0.3 and 1 mg/kg feed from hatching to 6 weeks of age. Total lymphocyte and T lymphocyte counts and the 2,4-dinitrofluorobenzene skin sensitivity test, graft-versus-host reaction and nitroblue tetrazolium salt reduction tests were used to evaluate CMI. Both doses of aflatoxin B1, including the apparently nontoxic dose of 0.3 mg/kg feed, caused a significant (P less than 0.05) decline in CMI. The functional activity of splenic macrophages was decreased significantly (P less than 0.05) by both doses of the toxin.

Immunosuppression due to chronic ochratoxicosis in broiler chicks.

Crystalline ochratoxin A (OA) was added to the feed of broiler chicks at 0.5 ppm and 2.0 ppm, and humoral and cell-mediated immunity (CMI) were studied. CMI was assessed by skin sensitivity testing, graft versus host (GVH) reaction and T lymphocyte count. Humoral immunity was examined by measuring the haemagglutinin (HA) response to sheep RBC (SRBC). In addition, total lymphocyte counts, total serum protein, albumin and globulin were determined and the phagocytic activity of splenic macrophages was measured in the nitroblue tetrazolium test (NBT). The weights of lymphoid organs were also recorded at post-mortem examination of the birds. Highly significant reductions in CMI were indicated by diminished skin sensitivity, GVH reactions and T lymphocyte counts. On the other hand, only the overall HA titres differed significantly between the various treatment groups. Total lymphocyte counts, total serum protein, serum albumin and serum globulin were significantly depressed on the 21st day of intoxication. The number of NBT-positive cells was drastically reduced in both the intoxicated groups compared with controls (P less than 0.05) and the weights of thymus, bursa of Fabricius and spleen of intoxicated birds were significantly reduced. The study illustrated the immunosuppressive effects of ochratoxicosis in broiler chicks.

In vivo and in vitro measurement of cell mediated immunity in Marek's disease: role of reticuloendothelial system.

Dinitrofluorobenzene (DNFB) contact-sensitivity test and leucocyte adherence inhibition (LAI) test were performed in this study as in vivo and in vitro tests to measure the cell-mediated immunity (CMI) in chickens subjected to stimulation of reticuloendothelial (RE) system, depletion of RE system and other experimental groups after being challenged with Marek's disease (MD) virus. It was found that CMI was lower in the birds with depleted RE system and infected control birds, whereas CMI was higher in the birds with activated RE system and vaccinated birds as revealed by DNFB contact-sensitivity test. In cases of LAI test, the number of LAI-positive birds were highest in the chicks with depleted RE system particularly in 3rd and 4th month of age, when the incidence of MD was also maximum.

Evaluation of cell-mediated immunity during chronic organophosphate pesticide intoxication in mice and goats.

The status of cell-mediated immunity (CMI) after pesticide exposure was assessed in mice with the help of skin sensitivity and graft versus host reaction tests. It was observed that at 24 hours post-challenge CMI values did not differ significantly from the control, indicating no effect of quinalphos treatment in mice. Goats receiving monocrotophos at a dose rate of 1.0 mg kg-1 body mass for 40 days gave a similar result when CMI was tested with the help of the chemical sensitizer dinitrofluorobenzene (DNFB). Thus the results clearly indicate that the tested organophosphates do not interfere with cellular immunity in the intoxicated animals.

The role of the reticuloendothelial system in the immunopathology of Marek's disease.

The role of macrophages in immunity against Marek's disease (MD) was studied. Chickens of one group were subjected to depletion of macrophages using repeated doses of Francil amorphous silica and those of another group were subjected to activation of macrophages using repeated doses of brewer's thioglycollate broth. Chickens of a third group were vaccinated with herpesvirus of turkeys FC 126 vaccine followed by depletion of macrophages. Chickens of these three groups, as well as groups of healthy unvaccinated and healthy vaccinated chickens, were challenged with virulent MD virus. A sixth group of healthy uninfected chickens was kept as a control. The results, based on clinical signs, gross and histopathological studies and agar gel precipitation test (AGPT) for antibodies, indicated that activation of macrophages enhanced immunity against MD and depletion of macrophages had the opposite effect. The protective effect of vaccination against MD was also lowered by depletion of macrophages. The results of AGPT indicated retardation of MD virus replication by macrophage activation and the reverse on depletion.

In vivo immunosuppression by synthetic pyrethroid (cypermethrin) pesticide in mice and goats.

Cypermethrin toxicity was produced in mice by intra-peritoneal injection of the pesticide at 50 mg/kg body weight per day for 26 days, and in goats by drenching with cypermethrin at 41.6 mg/kg body weight per day for 30 days. The status of cell-mediated immunity (CMI) was assessed by the 2,4-dinitrofluorobenzene (DNFB) skin sensitivity test. The results indicated significant depression of CMI in the cypermethrin-treated mice and goats. In addition, the humoral immune reaction of the goats intoxicated with cypermethrin was estimated by enumeration of the plaque-forming B-lymphocytes. The rate of plaque formation in the lymphocyte suspension of cypermethrin-treated goats was significantly reduced and the diameter of the plaques was also significantly lower than in that of control animals. The results indicated that cypermethrin suppressed both CMI and the antibody-forming ability of lymphocytes. This immunosuppressive action of cypermethrin is being reported for the first time.

Histopathology of the duodenum and rumen of goats during experimental infections with Paramphistomum cervi.

On microscopic examination after experimental infection with Paramphistomum cervi, tissue reactions in the duodenum were more pronounced during early stages of the infection (20th day post-infection (DPI)). Immature parasites were seen migrating to the muscularis layer, and focal infiltration of macrophages and lymphocytes was observed in the lamina propria and in the interstitial tissue of Brunner's gland. At places, there was cystic dilatation of Brunner's gland. At 40 DPI, the parasite was not present in the duodenal sections, and cellular infiltration was more diffuse and consistent. With the passage of time, the tissue reactions and cellular infiltration in the duodenum became less pronounced, but at 80 days parasites were attached to the villi of the rumen. Infiltration of mononuclear cells in the supporting connective tissue of the rumen was also observed. Thus, it is concluded that the immature forms of Paramphistomum cervi caused more severe damage in the duodenal tissue, whereas the adult form inflicted mild tissue damage in the rumen of the experimental kids.

Bone growth during chronic aldrin intoxication in goats.

Microscopic examination of the costochondral junction of goats after chronic aldrin intoxication revealed a drastic reduction in the width of proliferating, maturing and degenerating cartilage cells. The zone of provisional calcification was almost negligible in aldrin treated animals. In contrast, the control animals showed an orderly sequence of endochondral bone formation. Appositional bone growth studied by the tetracycline labelling technique also showed a marked reduction following chronic aldrin intake. It was concluded that decrease in the rate of appositional bone growth at endosteal periosteal and osteonic surfaces might be due to poor synthesis of bone matrix by the osteoblasts.