The aim of this project is to study the clinical signs and lesion of velogenic Newcastle disease (vND) in commercial turkeys, and also to find out if La Sota vaccination offered protection against these signs and lesions. The cockerels were included as positive controls. One hundred and twenty turkey poults and cockerels were divided into eight groups as follows: unvaccinated unchallenged turkeys (UUT), unvaccinated challenged turkeys (UCT), vaccinated unchallenged turkeys (VUT), vaccinated challenged turkeys (VCT), and along the same lines, the cockerel groups were UUC, UCC, VUC and vaccinated challenged cockerels (VCC). Vaccination was at 3 weeks of age while challenge was at 6 weeks of age. The unvaccinated turkeys and cockerels (UCT and UCC) showed different degrees of depression, diarrhoea and later paralysis at challenge. Total mortality was 100% in cockerels within 6 days, but 60% in turkeys. Similar but milder clinical signs were found in the VCC with a total mortality of 13.3%. The VCT showed mild drop in feed and water consumption, and no mortality. All the challenged groups had significant (p < 0.05) loss of weight when compared with their controls. Necropsy showed that while the UCC had severe proventricular haemorrhages, intestinal and caecal tonsil ulcers, the UCT had no digestive tract lesion. There was severe atrophy of the lymphoid organs in all the challenged groups. Histopathological sections of the bursa, spleen and thymus in all the challenged groups with special emphasis on the vaccinated and unvaccinated turkeys with mortalities of 0 and 60%, respectively, had very severe necrosis and depletion of the lymphoid tissue. Virus was isolated from the cloacal swabs. The haemagglutination inhibition antibodies were significantly higher (p < 0.05) in the challenged groups than the unchallenged. The above observations in the intestinal tracts of UCT are of diagnostic significance while the gross and microscopic lesions in the UCT and VCT show that La Sota vaccination may not protect turkeys against the destruction of the lymphoid organs by vND as earlier reported in chickens. This may lead to immunosuppression and production problems in areas where vND is enzootic.

To determine passive haemagglutination (PHA) antibody titer that would protect chicks against Nigerian isolates of the Infectious Bursa Disease Virus (IBDV), five groups of chicks aged 30 days which had different antibody titers were challenged with a Nigerian isolate of virulent IBDV. Mortality rates of the different groups were plotted against their respective mean PHA antibody titers. A group with zero antibody titer had a mortality rate of 75% while those with PHA antibody titers of 185.6, 243.2, 256 and 307.2 had mortality rates of 40%, zero, zero and zero respectively. Linear equation generated for a line of best fit of the graph of mortality rates of the chicks on their IBD antibody titers gave antibody titer (X) at which mortality (Y) would be zero as 300. A mortality of 75% and the high antibody level needed to protect chicks suggest that the isolate may be a hypervirulent strain.

An inexpensive and rapid test for determining titers of Human Immunodeficiency Virus (HIV) in plasmas was developed. Washed sheep red blood cells were applied onto HIV positive plasmas, in V-bottomed microtiter plates, to complement the HIV antigens and antibodies present in plasmas. The setup was incubated for 30 minutes at 37˚C. Reciprocal of the highest dilution of each plasma which gave passive agglutination of the RBCs was read as its HIV titer. Mean HIV load of five samples, was ≥ 4096.00 ± 0.00 after one day of storage at 4˚C but it reduced to 256.00 ± 70.10, 28.80 ± 3.20, 7.20 ± 0.80 and 1.60 ± 0.98 on days 2, 3, 4 and 7, respectively. HIV antibodies were still detectable, by ELISA, in plasma dilutions that were tested negative with the new test. It was concluded that when HIV antibodies have been confirmed, or added to plasmas, passive hemagglutination test can be applied to assess their viral loads.

This study compared the haematological findings in cockerels and turkeys infected with a velogenic Newcastle disease virus. One hundred and twenty day-old birds each of cockerels and turkeys, making a total of two hundred and forty were used for the study. The bird types were randomly divided into four groups each making a total of eight groups. Two groups in each species were vaccinated against NDV with La Sota vaccine at three weeks of age via drinking water. The vaccinated and unvaccinated cockerels and turkeys were inoculated with the velogenic NDV at six weeks of age while the control groups were not vaccinated and not inoculated. Blood samples were randomly collected from five birds in each group for haematological analyses at days 0, 3, 6, 10, 15 and 21 post inoculation (pi). The results showed significant (p < 0.05) reductions in packed cell volume, haemoglobin concentration and total red blood cell count in unvaccinated infected turkeys, but showed significant (p < 0.05) increase in total white blood cell (WBC) and heterophil counts throughout the days of the experiment. The increase in the total white blood cell counts was observed three days pi in the cockerels. There was reduction of lymphocytes in unvaccinated but infected cockerels and turkeys three days pi. The erythrocyte and leukocyte values in unvaccinated but infected cockerels and turkeys were similar. The values were lower than those recorded in vaccinated and infected birds. Thus, vaccination against the disease can ameliorate the adverse effect of the virus on haematological parameters. Vaccination of the birds against velogenic Newcastle disease virus reduced morbidity and mortality.

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