DIFFERENTIAL-DIAGNOSIS OF THE COMMONEST B ACTERIAL DISEASES OF YOUNG GEESE

In 1996 in the first five months of 1997 a total of 3479 day-old gosli ngs were examined at the Central Veterinary Institute. The commonest f indings were poor viability and growth retardation (Table 1). Of the b acterial diseases, paratyphoid was the most common, followed by coliba cillosis and streptococcosis. A total of 2686 young goslings aged 1-8 weeks were examined in the period of study. The most frequent diagnosi s was Derzsy's disease (Table 2). In the order of their incidence, the most frequent bacterial diseases were paratyphoid, mycoplasmosis, str eptococcosis, colibacillosis, chlamydiosis, anatipestifer syndrome, an d septicaemia caused by the erysipelas bacterium (Erysipelothrix rhusi opathiae). The clinical symptoms of the above-mentioned infectious dis eases are summarised in Table 3, while the gross lesions and histopath ological changes caused by them in Table 4. According to the authors' observations, anatipestifer syndrome usually occurred at the age of 2- 3 weeks. Morbidity and mortality were around 2-5%. The affected goslin gs exhibited nervous symptoms (Figure 1). At necropsy, fine, hardly no ticeable fibrin precipitation was seen in the pericardium, on the air sacs, and occasionally on the serosal surface of the liver and the oth er abdominal organs. Histopathological examination revealed the diffus e thickening of the leptomeninges covering the brain and spinal cord, their infiltration by inflammatory cells including histiocytes, lympho cytes and heterophilic granulocytes (Figure 2), and their serofibrinou s imbibition. By bacterial culture Pasteurella anatipestifer (or, acco rding to the recently proposed name, Riemerella anatipestifer) bacteri a were isolated from the goslings showing nervous signs and from the d ead birds. Mycoplasmosis occurred in young goslings, usually at 3-4 we eks of age. Morbidity was usually between 15 and 25% while mortality w as 3-8%. At necropsy, deposition of fibrin was consistently seen on th e surface of the air sacs and on the pericardium. Histopathologically, focal infiltration was observed in the epicardium, in the wall of the pericardium and the air sacs and, here and there, also in the serosa covering the lungs. Mononuclear cell infiltration of proliferative typ e (Figure 4) was detected in the lungs as well as in the wall of the p arabronchi and air capillaries. The pathogen is easily recognisable by electron microscopy (Figure 5). Mycoplasma strain 1220 was most commo nly detectable from this disease entity. Chlamydiosis occurred mostly in 3-4 weeks old goslings. Gross pathologically it was characterised b y the presence of a few small necrotic foci in the liver and spleen. B y histopathological examination, necrotic and inflammatory-necrotic fo ci could be recognised in the liver (Figure 6). The pathogens are dete cted by Stamp's staining as well as by immunofluorescence (Figure 7) a nd by an immunohistochemical method. By ultrastructural examination ro und elementary bodies and so-called reticulate bodies of larger size, loosened structure and containing nuclear primordia can be seen (Figur e 8.) Streptococcosis was the most common in gosling of 2-3 weeks of a ge. At necropsy, the spleen was 3 or 4 times its normal size, compact to the touch, and showed 3 regular mottled pattern on its cut surface (Figure 9). The liver nas invariably swollen, with numerous necrotic f oci and haemorrhages on its surface and cut surface (Figure 10). Histo pathological examination of the spleen and liver showed circumscribed or extensive necroses in which coccus-shaped bacteria could be recogni sed by Gram staining. The pathogen could be isolated in exuberant cult ures from the bone marrow, spleen, liver, bile, kidney, heart blood, b rain, pancreas and even from the intestinal lumen. Salmonellosis was s een both in day-old goslings and in growing geese. Necropsy; revealed the formation of thick fibrinous pseudomenbranes on the serosae of the thoracic and abdominal cavity (Figure 12), swelling of the liver and spleen (Figure 13), and acute enteritis. Fibrinous inflammation of the caecum and rectum, characterised by the formation of fibrin plugs, wa s also commonly encountered (Figure 14). The typing results of Salmone lla strains isolated from geese in the period of study are shown in Ta ble 5. Septicaemia caused by E. coli (coli septicaemia, colibacillosis ) occurred both in day-old and in growing geese, but was less common t han salmonellosis. In flocks of growing geese it was usually seen as a complication of other diseases. Septicaemia caused by Erysipelothrix rhusiopathiae is a relatively common condition in adult geese. It occu rs mainly after plucking or as result of other major stress factors im pairing the birds' natural resistance. In young (5-6 weeks old) flocks it was observed only once in the study period. Clostridium septicum i s one of the causative agents of malignant oedema in mammals. It rarel y causes disease in poultry species. Such diseases have been described only in chickens and turkeys in the special literature. At our instit ute, disease and deaths caused by Cl. septicum were diagnosed in 5-6 w eeks old gosling flock.