Suspected pox virus infection of a Dunlin

On 7th January 1967, at the Point of Air, Flintshire, I found a Dunlin Calidris alpina which could fly only for short distances before landing awkwardly and running with difficulty. It was easy to catch and proved to have a large tumour-like growth around the tibiotarso-tarsometatarsal joint of the right leg (plate 8a, left). It died shortly after. Dissection showed no obvious internal disease, but there was marked reduction of subcutaneous fat and many parasitic worms were noted in the gut. Besides the leg growth the only other lesion found was a nodule measuring 20 x 10 x 5 mm on the lower external abdominal wall. The leg lesion measured 25 x 20 x 25 mm and the amputated leg weighed 6.4 grams. The normal left leg amputated in a similar manner (plate 8a, centre) weighed 0.7 grams. Bisection of the growth revealed a creamy-white cut surface with many cystic spaces filled with turbid fluid (plate 8a, right). Histological examination of this and of the abdominal nodule showed the typical appearance of infection with pox virus. There was great proliferation of the skin epithelium and the cells contained intra-cytoplasmic acidophilic inclusion bodies. The cystic spaces were formed by the necrotic breakdown of the infected cells. Dr I. F. Keymer kindly examined some of the sections and he agreed {in litt.) that the changes were similar to those seen in pox infections, particularly pigeon pox. The Dunlin was in winter plumage and the measurements taken were bill } 2 mm, wing 116 mm and weight 44 grams. Dissection showed it to be a male and the measurements indicate the northern race C. a. alpina.