Swinepox dermatitis in backyard pigs in Northeastern Brazil

摘要

: This article describes five outbreaks of swinepox in backyard pigs in Northeastern Brazil. It affected backyard pigs from herds of poor hygienic-sanitary conditions with severe fly and lice infestations. The morbidity ranged from 33.3 to 100% among affected herds, with mortality reaching up to 60%. The affected pigs developed multifocal to coalescent gray to white papules and blisters in the skin, with eventual eruptions, evolving to erosions and crusts. In addition to skin lesions, affected piglets presented apathy, anorexia and fever. The disease was auto-limiting, resolving within 15 to 25 days. Histological examination revealed proliferative and ulcerative vesiculopustular dermatitis with ballooning degeneration of epithelial cells, perivascular inflammatory infiltrates of lymphocytes, plasma cells, neutrophils, eosinophils and some macrophages in the dermis. Intracytoplasmic eosinophilic inclusions were consistently observed in keratinocytes. Total DNA extracted from fresh tissue fragments obtained from one outbreak and formalin-fixed, paraffin-embedded (FFPE) tissue from the other four outbreaks was submitted to polymerase chain reaction (PCR) for Swinepox virus (SWPV) and Vaccinia virus (VACV). Genetic SWPV material was identified by PCR in fresh material from one outbreak. Nucleotide sequencing and phylogenetic analysis of the PCR amplicons (viral polymerase gene) demonstrated 100% homology with sequences from SWPV. All tissues were PCR negative for VACV. Swine poxvirus is present in backyard pigs in Northeastern Brazil, indicating the need of including SWPV in the differential diagnosis of dermatitis in pigs. Index Terms:??Swine; poxvirus; dermatitis; viral disease Resumo: Em cinco surtos de var?-ola em su?-nos no Nordeste do Brasil foram acometidos leit?μes e su?-nos adultos, de rebanhos dom??sticos criados em condi?§?μes higi?anico-sanit??rias prec??rias, que apresentavam graves infesta?§?μes por moscas e piolhos. A morbidade variou de 33,3-100% entre os rebanhos afetados e a mortalidade atingindo 60%. Os animais afetados desenvolveram p??pulas cinzentas ou esbranqui?§adas coalescentes e ves?-culas, que evolu?-ram para eros?μes e crostras. Al??m das les?μes de pele, os leit?μes afetados apresentavam apatia, anorexia e febre. A doen?§a foi autolimitante, com resolu?§?￡o em 15 a 25 dias. Histologicamente, observou-se dermatite proliferativa e ulcerativa com degenera?§?￡o balonosa das c??lulas do epit??lio, infiltrado inflamat?3rio perivascular de linf?3citos, plasm?3citos, neutr?3filos, eosin?3filos e escassos macr?3fagos na derme. Inclus?μes eosinof?-licas intracitoplasm??ticas foram consistentemente observadas em queratin?3citos. DNA total extra?-do a partir de fragmentos de tecido frescos obtidos a partir de um surto, e de tecido fixado em formol e embebido em parafina dos outros quatro surtos, foram submetidos ?? rea?§?￡o em cadeia da polimerase (PCR) para o v?-rus da var?-ola su?-na (SWPV) e o v?-rus vacc?-nia (VACV). Material gen??tico do SWPV foi identificado por PCR em material fresco de um surto. O sequenciamento e an??lise filogen??tica dos produtos de amplifica?§?￡o da PCR (gene da polimerase viral) demonstraram 100% de homologia com sequ?ancias do SWPV. Todos os fragmentos de tecidos foram negativos para VACV na PCR. Este artigo relata a circula?§?￡o de poxv?-rus su?-no no Nordeste do Brasil, indicando a necessidade de incluir SWPV no diagn?3stico diferencial de dermatite em su?-nos. Termos de Indexa?§?￡o:??Su?-no; var?-ola; dermatite; doen?§a viral Introduction Swinepox is a vesiculopustular disease of young and adult pigs caused by Swinepox virus (family Poxviridae, genus Suipoxvirus) (Afonso et al. 2002). Affected pigs present progressive and frequently generalized lesions in the skin, starting with petechiae. These petechiae evolve through the stages of papules, vesicles and yellow pustules that eventually originate crusts (scabs) with crateriform aspect (Munz & Dumbell 1994). The clinical course is approximately four weeks, but lesions may persist longer in pigs under poor hygienic conditions due to secondary bacterial and parasitic infections (Bersano et al. 2003, Medaglia et al. 2011). Pigs are apparently the only host species of SWPV in nature and virus transmission is usually associated with poor hygienic conditions and the presence of insects, mainly lice (Haematopinus suis) and domestic flies (Musca domestica) which act as mechanic vectors for virus transmission (Munz & Dumbell 1994). The virus is usually transmitted by direct or indirect contact. Congenital infection resulting in newborn piglets with generalized lesions may sporadically occur (Paton et al. 1990). Although the mortality is generally low, the morbidity in affected herds may reach up to 100%. Piglets are most frequently affected and present more severe lesions than adult animals (Bersano et al. 2003). In general, the disease is restricted to the skin, with preference to less keratinized regions such