A model of pneumonic pasteurellosis has been established in goats using Pasteurella multocida harvested from pneumonic lungs of goats (types A and D), rabbits (type A) and sheep (type D). The resultant infections were acute, subacute or chronic. The gross and histological lesions of the subacute and chronic infections were typical of pneumonic pasteurellosis. P. multocida type D produced significantly (P < 0.01) more severe lesions when compared with other isolates. There were strong correlations between the clinical signs and the severity of lesions.
The effectiveness of an oil adjuvant vaccine (OAV) incorporating locally isolated strains of Pasteurella haemolytica type 7 and Pasteurella multocida types A and D was compared with that of Carovax (Wellcome Laboratories) in imported cross-bred lambs. The criterion of efficacy was the ability of the vaccines to reduce the extent of pneumonic lesions in vaccinated as against unvaccinated control lambs. The OAV produced at this Institute significantly reduced the lung lesions at P less than 0.05 level compared with its control group when challenged with P. haemolytica alone. However, the vaccine was unsatisfactory against P. multocida or combined P. multocida P. haemolytica challenge. Carovax did not produce any significant reduction in the lung lesions caused by P. haemolytica and/or P. multocida.
Two groups of goats were dosed with 20,000 and 40,000 sheep-derived strain (SDS) larvae of Trichostrongylus colubriformis respectively. Over a period of 42 days, goats dosed with 40,000 larvae lost more weight than goats dosed with 20,000 larvae. Anaemia was not observed in infected goats, but total serum proteins, albumins and phosphorus fell with infection.
Two groups of goats were dosed with 10,000 and 20,000 sheep-derived strain (SDS) larvae of Haemonchus contortus respectively. Over a period of 42 days goats dosed with 20,000 larvae lost more weight than those dosed with 10,000 larvae. Infected goats showed anaemia from about 2 weeks after infection as well as reduced levels of total serum proteins and albumins.
Two groups of goats were experimentally infected with Haemonchus contortus and Trichostrongylus colubriformis, and killed at various days after infection (DAI). The percentage of worms that established in the abomasum and the small intestine was low. At necropsy, abomasums from infected goats had thickened walls and oedematous folds. At 7 DAI there was an initial infiltration of eosinophils and some neutrophils which tend to increase with age of infection. The mean pH of the abomasum in goats infected with H. contortus was 5.43 (range 5.3-5.7), while that of the control goats was 3.30 (range 2.8-3.7).
Sixteen goats either subjected to transport stress or without transport stress were treated with dexamethasone for 3 days prior to infection with P. haemolytica serotype A2 intranasally. The transport-stressed and dexamethasone-treated goats in the first group had various degrees of pulmonary lesions and the organism was re-isolated from the nasal cavity, lymph nodes and lungs. None of the goats treated with dexamethasone only were infected with P. haemolytica and had no lesions of pneumonic pasteurellosis. Treatment with dexamethasone alone failed to induce experimental infection by P. haemolytica except in combination with another stress factor.
Twenty transport-stressed goats were divided into two groups. The first group was further stressed with steroid. Pasteurella haemolytica was found at various sites in the nasal cavity of goats in this group as early as 2 weeks post-transportation. The successful isolations continued consistently with more goats having pure growth of P. haemolytica at later stages. Mild catarrh rhinitis, loss of epithelial cilia and erosions were the main lesions observed in the nasal cavity. Goats in the second group that were not given steroid injections had inconsistent bacterial isolation and less severe pathological lesions.