Veterinary Services

Poultry

Elevated mortality was reported in a small flock of 5000 broilers. Postmortem examinations at five days of age showed evidence of yolk sac infection, pericarditis and perihepatitis associated with E coli. Further necropsies at 17 days revealed pericarditis, perihepatitis, splenomegaly and airsacculitis, again associated with E coli. Similar changes were seen at 30 days, by which time increased culling due to septic arthritis and tenosynovitis was occurring. The underlying factor or factors predisposing to the E coli infection were not determined.

Three adult turkeys from a small free-range flock were found dead within 24 hours. All three showed severe unilateral or bilateral pneumonitis and pleuritis and heavy growths of Pasteurella multocida were cultured. Losses from pasteurellosis occurred on this site two years earlier.

Marek’s disease was diagnosed in an adult male show silkie that developed unilateral leg paralysis. Enlargement of one sciatic nerve was noted at necropsy, and histopathology demonstrated prominent foci of lymphocytic infiltration in both sciatic nerves and both brachial nerves. Pure-bred silkies appear to be especially susceptible to Marek’s disease. This particular bird was vaccinated at day-old and the SAC considers that exposure to Marek’s disease virus from the environment occurred before protective immunity from the vaccine developed. A sibling of the affected bird had developed similar clinical signs but had recovered following treatment with an anti-inflammatory agent. The transient paralysis form of Marek’s disease possibly affected that bird.

Game birds

One of the commonest conditions diagnosed in game birds in recent years was infection with the motile protozoan organism Spironucleus (Hexamita) meleagridis. Spironucleosis results in weight loss, diarrhoea and death in pheasants and red-legged partridges, especially in the months June to September. Historically this disease was controlled by the inclusion of dimetridazole in the feed but the marketing authorisation for this product was suspended in 2002. Currently there is no product with a marketing authorisation for the treatment or control of spironucleosis in game birds.

Figure 3 (see top right-hand side) shows the numbers of game bird submissions to SAC and VLA in which a diagnosis of spironucleosis was made over the past 10 years. A cyclical pattern may be emerging, with a peak in 2000 (prior to the loss of dimetridazole) falling to a low in 2004 and now building to another peak. The impact of the suspension of dimetridazole is unclear.

When the data are re-examined to take into consideration the effect of total submission numbers, a similar pattern can be seen, with spironucleosis diagnosed in an increasing percentage of game bird submissions received in the past three years (figure 4 - see top right-hand side). The monthly pattern of spironucleosis incidents in the past three years is presented in figure 5 (see top right-hand side). Most incidents occurred in the months June to September, but the increase in incidents observed in 2007 was largely due to a greater number of incidents in August and September.

If the trend observed in recent years continues into 2008, game bird rearers and their veterinary advisers should be aware that spironucleosis is likely to remain a significant problem, especially in the months August and September. In the absence of appropriate medication, control depends on improved hygiene, increased biosecurity, reduced stocking density and the adoption of other management practices that reduce stress.

Pigeons

Large numbers of hairworm eggs were detected in pooled faeces from a loft in which several birds had green mucoid faeces. In a different loft three adult stock birds died. Postmortem examination of the submitted bird revealed fluid mucoid intestinal contents, and similar to the first loft, large numbers of hairworms and their eggs were demonstrated in the intestinal contents and faeces.

Wild birds

Salmonellosis was diagnosed in garden birds from nine sites. As in previous years, Salmonella Typhimurium DT 40 predominated in the north of Scotland and S. Typhimurium DT 56 variant was the commonest isolate in the south of Scotland. Unusually for Scotland, the commonest species affected was the siskin (Carduelis spinus) (five sites), with the chaffinch (Fringilla coelebs), goldfinch (Carduelis carduelis), greenfinch (Carduelis chloris) and dunnock (Prunella modularis) affected on single sites. This may represent a change in feeding practices by the general public, attracting more siskins to bird feeding stations. An isolate of S. Typhimurium DT 120 was considered to be an incidental finding in a blue tit (Parus caeruleus).