How to cite: Sawale, G. K., Lakshman, M., Hanumanthrao, M., Balaeswara Raju, B. V. & Ramesh, G. (2019). Pathology of Avipoxvirus in Turkey: Histopathology, Cytology and Electron Microscopy Study. International Journal of Livestock Research, 1(10), 179-184. doi: 10.5455/ijlr.20181009023808

Introduction

Avian pox viruses affect commercial poultry viz. fowl and turkey, as well as several other avian species and are the members of the genus Avipoxvirus of the family Poxviridae (Tripathy and Reed, 2008). Avipoxvirus genus includes fowl pox, turkey pox, pigeon pox, quail pox and canarypox as major viral strains (Singh et al. 2003). Turkey poxvirus represents the type species of the genus avipoxvirus (Mathews, 1982). Pox diseases in chickens and turkeys are characterized by the development of proliferative lesions, ranging from small nodules to spherical wart-like masses on the skin (cutaneous form /dry pox), comb, wattle and other non-feathered part of the body (Riper and Forrester, 2007; Tripathy and Reed, 2008 ).

The avian pox rank among the earliest poultry disease that has identified. Heusinger (1844) described the external (gross lesions) features of the disease. Subsequently, Bollinger (1873) and Borrel (1904) described the correlation between the histological lesion and inclusion body, a characteristic feature of the disease. A detail description of inclusion bodies and confirmation avian poxvirus was demonstrated by Woodruff and Goodpasture (1930). The detail reports and studies on gross pathology, histopathology and electron microscopy has been described in avian and wild birds in world literature. The pathology of fowlpox has been well described worldwide (Riper and Forrester, 2007; Tripathy and Reed, 2008; Banyai et al., 2015). In India, a detail description on the clinical sign, lesion distribution and histopathology of avian pox and isolation of virus have been described (Sawale et al., 2012). Singh et al. (2003) isolated and characterized Indian isolates of turkey pox virus along with electron microscopic features of the virus.

Although pathology of avipox has been described in world literature, the study on turkey pox is meagre. Hence, present communication reports on the occurrence of pox in turkey of broad breasted white variety type and its cytology, pathology and Transmission Electron Microscopy (TEM) study.

Case History

Five dead turkeys of broad breasted white variety type of two months age were presented from the Department of Poultry Science, College of Veterinary Science, Rajendranagar to the Department of Veterinary Pathology for necropsy. The detail necropsy of dead turkeys was conducted and gross lesions were recorded. Turkey pox was suspected on the basis of the clinical signs and gross lesions observed. The scab from the skin as well as other visceral organs like liver and kidneys were collected and fixed in 10 % neutral buffer formalin for 72 hours, processed and embedded in paraffin blocks. Section of 5 µm was taken on slides and stained with haematoxylin and eosin (H & E). A small piece of scab (0.5mm³) was preserved in 2.5 % glutaraldehyde prepared in 0.1M phosphate buffer saline for Transmission Electron Microscopy (TEM). Transmission Electron Microscopy was performed as per the method described by Lakshman (2016). Scab of dead turkeys, as well as other affected turkeys (six), were collected. An impression smear was prepared from the cut surface of scab, fixed with absolute methanol and stained with the standard protocol of Giemsa-Leishman stain. The Giemsa-Leishman staining was performed by pouring a few drops of stain till overlaying of smear and kept for one minute. Then an equal quantity of distilled water was added on smear containing stain and mixed properly by dropper and kept for 15 minutes. The smear was then washed with tap water, air dried and observed under the light microscope.

Clinically, turkey birds showed dullness, inappetence and lethargy before death. The total mortality was 3.33 (5 out of 150 turkey birds) per cent and the flock was un-vaccinated against turkey poxvirus. Necropsy of the dead turkeys showed numerous circular to irregular size raised nodules of 1-3 cm in diameter on the skin of the head, eyelid and around the beak. Lesions were primarily confined to non-feathered parts of the body viz. head and beak (Fig. 1).

Fig. 1: Turkey bird showing nodular growth on head, and around nostril

Liver and kidneys showed vascular congestion with prominent ureter due to urate deposition. Histopathological examination of scab revealed hyperplasia of the epidermis and severe balloon degeneration with intra-cytoplasmic, eosinophilic inclusion bodies (Fig. 2). At few places, a section of the skin showed few colonies of bacteria (Fig 3) as well as numerous heterophilic and sparse lymphocytic infiltration.

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