Spirocercosis in stray dogs of Chittagong Metropolitan area of Bangladesh: an epidemiological and pathological investigation

A total of sixty adult stray dogs (32 male and 28 female) randomly captured from different locality of Chittagong metropolitan area were euthanized during the period of May 2010 to January 2011. The dogs were necropsized to observe the presence of Spirocerca lupi in their oesophagus producing characteristic nodular lesions. The associated haematological changes were also determined. Twenty four (40%) of the captured dogs were positive (40.62 % male and 39.28 % female) for spirocercosis having oesophageal nodular lesions. One to three broad based nodular lesions with an average diameter of 2.104 +/- 0.139 cm were observed in the caudal oesophagus of spirocerca positive dogs. Minimum 1 and maximum 12 worms found harboring in each nodule with an average number of 3.75 +/- 0.686. The association between the oesophageal nodular lesions and body condition of the dogs was inconclusive and locationwise prevalence was also not clear. Anaemia was observed in infected dogs with significant reduction in ESR values and MCHC%. Leukocytosis, particularly neutrophilia was common in infected dogs in comparison to the noninfected. Histopathology revealed extensive fibrous tissue proliferation around the adult worms in most of the nodular lesions with large numbers of newly formed blood vessels resembling granulation tissues. A considerable degree of fibroplasia was evident with predominant accumulation of fibroblasts and irregular layers collagen fibers in mature nodules. Accumulation of large numbers of neutrophil was common in nodular lesions, whereas, infiltration of lymphoplasmacytic cells also found in some cases. One lesion showed evidence of fibrosarcoma characterized by proliferation of undifferentiated atypical fibroblasts having abnormal mitotic figures.