Experimental induction of an immunohaemolytic anaemia in the chicken with Salmonella gallinarum endotoxin.

The possibility that the extreme refractoriness of the chicken to injected endotoxin would permit the buildup of sufficient free endotoxin in the circulation to immunologically modify the erythrocytes in vivo and thereby cause them to be eliminated from the circulation was investigated. It was shown that a moderately severe immunohaemolytic anaemia accompanied by a mild spenomegaly could be induced in chickens by single (large) or multiple injections of Salmonella gallinarum endotoxin (SgE). Varying degrees of reticulocytosis, with corresponding decreases in haemoglobin and haematocrit values, were observed from the tenth day after the injection of the SgE. All the injected animals also showed significant immune responses to SgE, peak haemagglutinin titres occurring coincidentally with the peaks of the haemolytic episodes. A similar injection schedule in specifically immune chickens also showed the anaemia appearing much earlier, persisting longer and being much more profound in intensity. It is considered that the in vivo erythrocyte sensitization induced by SgE injection initiates the erythrocytic changes observed and that the underlying mechanism responsible for the subsequent development of the haemolytic anaemia is immunologically mediated.     

Detection of antibodies to platelets and erythrocytes during infection with haemorrhage-causing Trypanosoma vivax in Ayrshire cattle

Ayrshire cattle, which were infected with a stock of Trypanosoma vivax from Galana, Kenya, which produced haemorrhagic disease, were examined for the presence of antibodies to erythrocytes and platelets. Antibodies to normal erythrocytes and platelets were detected in the plasma of infected animals using the enzyme-linked immunosorbent assay (ELISA). The antibodies were detectable following the first peak of parasitaemia (10-15 days after infection) and antibody activity was maximal 30-35 days after infection. Plasma from cattle, taken 32 days after infection, precipitated radiolabelled proteins from autologous platelets and, less efficiently, from autologous erythrocytes. Fluorescence-activated cell sorter (FACS) assays demonstrated that erythrocytes and platelets from infected cattle bound IgM and IgG in vivo, and that both normal blood cell types could adsorb these antibodies following incubation in plasma from infected animals. Complement (C3) was similarly adsorbed to erythrocytes during infection. Antibodies adsorbed to infected erythrocytes could be eluted and the eluted antibodies bound to normal erythrocytes, as detected by immunofluorescence, but they did not react with the infecting trypanosome. It is hypothesised that although anti-blood cell antibodies may not be the primary cause of the severe anaemia and thrombocytopaenia which accompany the haemorrhagic syndrome, they could play an important role in the maintenance of these signs of disease, adversely affecting the outcome of T. vivax-associated haemorrhagic disease in the field.     

Oocyst Counts in Crossbred Ewes under Tree-Crop Plantation in the Forest Zone of Ghana

In this paper, the Eimeria oocyst output of two groups, pregnant ewes (group 1) and non-pregnant controls (group 2), which were followed from September 1993 to August 1994, is described. In both groups of animals the level of oocyst output was high during the minor rainy season. However, during the periparturient period the pregnant ewes showed the higher oocyst output. The oocyst output in both groups fell to similar levels after weaning of the lambs in March 1994. The species of Eimeria identified in order of dominance were Eimeria parva, E. pallida, E. faurei, E. ahsata, E. ovina, E. intricata, E. granulosa and E. ninakohlyakimovae. There were no differences in the species composition of oocysts in both groups of animals.     

Haemorrhagic lesions resulting from Trypanosoma vivax infection in Ayrshire cattle

Infection of Ayrshire cattle with a stock of Trypanosoma vivax from the Galana Ranch, Kenya, resulted in an acute disease characterised by profound anaemia and haemorrhage, which reached maximum severity between 3 and 5 weeks after infection. Bleeding from the ears, nose and rectum occurred. At necropsy, petechial and ecchymotic haemorrhages were widespread, but were particularly severe in the gastrointestinal tract. In confirmation of the gross findings, congestion, haemorrhage and degenerative changes in most tissues and organs were found histologically. Thrombi were seen in the lymphatic vessels and clots of fibrin were present in the ventricles of the brain. The anaemia was a consequence of frank blood loss through haemorrhaging, exacerbated by erythrophagocytosis of deformed red blood cells, whose occurrence was indicative of microangiopathic changes. Animals were euthanised between 23 and 36 days after infection when they became recumbent with PCV values as low as 9%. There is no doubt that animals affected by this syndrome in the field would die within a few weeks of infection, if left untreated.     

Observations on Strains of Salmonellae Recently Isolated from Domestic Animals in Ghana

Tropical Animal Health and Production - Fifteen different serotypes of salmonellae, identified from forty-one strains of salmonellae recently isolated from domestic animals at post mortem...