An outbreak of malignant catarrhal fever in Sambar deer (Rusa unicolor)

Dacryoadenitis caused by Cochliomyia macellaria (Diptera: Calliphoridae) in a sambar deer (Rusa unicolor) in Rio de Janeiro, Brazil

Flies of the genus Cochliomyia frequently cause myiasis in the Americas during the hot and humid climate, which favors the development of the parasite's life cycle. A three-year-old female sambar deer (Rusa unicolor), originated from a conservation farm in the municipality of Casimiro de Abreu, Rio de Janeiro state, Brazil, was presented for a necropsy. Grossly, a nodular wound in the right lacrimal gland was observed, with many intralesional larvae. The histopathological evaluation of the injured lacrimal gland revealed maggots surrounded by areas of necrosis and inflammation. Specimens were collected for parasitological examination. Morphologically, larvae were identified as Cochliomyia macellaria (Diptera: Calliphoridae). It is suggested that adult C. macellaria was attracted to the site of infestation by glandular secretion. The present study shows the first report of secondary myiasis by Cochliomyia macellaria in deer.

A review of the epidemiological, clinical, and pathological aspects of malignant catarrhal fever in Brazil

Sheep-associated malignant catarrhal fever (SA-MCF), the form of MCF that occurs in Brazil, is a severe, frequently fatal, infectious disease caused by ovine gammaherpesvirus-2 (OvHV-2), in which sheep are the asymptomatic hosts and cattle and other cloven-hoofed animals are the accidental hosts. This review provides a critical analysis of the historical, epidemiological aspects and the estimated economic impacts associated with SA-MCF in Brazil. Moreover, the clinical manifestations and pathological lesions associated with SA-MCF in cattle are reviewed and discussed and the phylogenetic distribution of OvHV-2 in Brazil is presented. OvHV-2 is the only MCF virus identified in animals from Brazil. It is recommended that a histopathologic diagnosis of SA-MCF be based on all aspects of vascular disease in the affected animal and not only lymphocytic/necrotizing vasculitis and/or fibrinoid change. Conformation of the intralesional participation of OvHV-2 in these alterations can be achieved by immunohistochemistry and/or in situ hybridization assays. Additionally, it is proposed that OvHV-2 should be considered as a possible infectious disease agent associated with the development of bovine respiratory disease in cattle. Furthermore, the possible role of the small intestine in the dissemination of OvHV-2 is discussed.

Malignant Catarrhal Fever in Cattle in the Irkutsk Region

Introduction

Malignant catarrhal fever (MCF) is a rare, under-explored lethal viral infection of cattle with gammaherpesvirus aetiological agents. Most often, the disease occurs on farms where cattle and sheep are kept together. However, other trigger mechanisms and environmental factors contribute. This study investigates the causation of MCF.

Material and Methods

An outbreak of MCF occurred in June - August 2017 in Kharchev village in Irkutsk Oblast, Russia. In this paper, we provide epidemiological (sanitary status of pastures, watering places, and premises) and weather data during the outbreak, and descriptions of the clinical signs and post-mortem changes in cattle. The virus was detected and isolated from pathological material samples and identified by molecular methods.

Results

Extreme weather conditions, mixed-herd cattle and sheep farming, and unsatisfactory feed quality contributed to the outbreak. A virus related to herpesvirus OvHV2 was isolated and typed (MCF/Irkutsk/2017). Phylogenetic analysis showed its close genetic relationship to isolates from cattle and sheep in Germany, USA, and the Netherlands.

Conclusion

Sporadic outbreaks of MCF caused by biotic and abiotic factors together are typical for the Russian Federation, and the Irkutsk outbreak epitomised this. Temperature anomalies caused pasture depletion, resulting in feed and water deficiency for grazing animals and dehydration and acidosis. Heat stress in animals ultimately led to the occurrence of MCF in the herd.