Swinepox dermatitis in backyard pigs in Northeastern Brazil

Abstract

RESUMO.-[Varíola em suínos no Nordeste do Brasil.]Em cinco surtos de varíola em suínos no Nordeste do Brasil foram acometidos leitões e suínos adultos, de rebanhos domésticos criados em condições higiênico-sanitárias precárias, que apresentavam graves infestações por moscas e piolhos. A morbidade variou de 33,3-100% entre os rebanhos afetados e a mortalidade atingindo 60%. Os animais afetados desenvolveram pápulas cinzentas ou esbranquiçadas coalescentes e vesículas, que evoluíram para erosões e crostras. Além das lesões de pele, os leitões afetados apresentavam apatia, anorexia e febre. A doença foi autolimitante, com resolução em 15 a 25 dias. Histologicamente, observou-se dermatite proliferativa e ulcerativa com degeneração balonosa das células do epitélio, infiltrado inflamatório perivascular de linfócitos, plasmócitos, neutrófi-los, eosinófilos e escassos macrófagos na derme. Inclusões eosinofílicas intracitoplasmáticas foram consistentemente observadas em queratinócitos. DNA total extraído a partir de fragmentos de tecido frescos obtidos a partir de um surto, e de tecido fixado em formol e embebido em parafina 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.

Primary skin diseases and cutaneous manifestations of systemic diseases in swine

“…Swinepox corresponded to 5.8% of our diagnoses, in a study on swine diseases, it corresponded to 0.2% of the infectious and parasitic diseases diagnosed (Brum et al 2013). This disease is caused by a poxvirus, has a wide distribution and outbreaks have already been described in São Paulo (Bersano et al 2003, Medaglia et al 2011, Tocantins (Bersano et al 2003), in the Brazilian northeast (Olinda et al 2016), Italy (Mariano et al 2015) and India (Mech et al 2018). The histological aspects were similar to those described by Olinda et al (2016), of the nine cases, in eight, viral infection was associated with histological lesions suggestive of allergic dermatitis, suggesting the theory that Haematopinus suis lice and flies may be mechanical vectors for the transmission of the swinepox virus (Torrison & Cameron 2019).…”

First Report of Swinepox in a Wild Boar in Italy: Pathologic and Molecular Findings

“…The most readily visible histological changes of tissues from swinepox-infected pigs include hydropic degeneration of the epidermal stratum spinosum and keratinocytes, where viral replication occurs [ 1 ]. Eosinophilic, rounded, intracytoplasmic inclusion bodies 3–8μm in diameter can be observed in keratinocytes [ 9 , 12 ]. Indeed, the histological analysis of the lesions from the neck and ear skin of the described case showed keratinocyte degeneration at this level, with intracytoplasmic eosinophilic inclusions ( Figure 2 ).…”

“…In two outbreaks in the northeast of India, the entire body of the affected animals was found to be heavily infected with swine lice [ 7 ]. Similarly, in five swinepox outbreaks in northeastern Brazil, affected backyard pigs from herds with poor hygienic conditions presented with severe fly and lice infestations [ 12 ]. In contrast, in an outbreak described in Papua New Guinea, lice were not observed, but a large number of stable flies, Stomoxys calcitrans , was present.…”

“…Its main mode of transmission is through the biting of the pig louse Haematopinus suis , which acts as a mechanical vector; however, direct animal contact and congenital transmission have also been reported [ 2 , 3 , 4 ]. Swinepox was first described as a disease of domestic pigs in Europe in 1842 [ 5 ] and in the USA in 1929 [ 6 ], but outbreaks have subsequently been found in pigs also in Africa, Asia, Australia and South America [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. It is commonly associated with poor sanitation [ 4 ], since the virus shows a high environmental stability and is very resistant to drying, as all poxviruses are [ 14 ].…”

Swinepox Virus Strains Isolated from Domestic Pigs and Wild Boar in Germany Display Altered Coding Capacity in the Terminal Genome Region Encoding for Species-Specific Genes

“…This virus contains a linear double-stranded DNA genome of 146 kbp and is the etiological agent of an eruptive dermatitis in pigs, known as swinepox. Swinepox was first described as a disease of domestic pigs in Europe in 1842 [1] and in the USA in 1929 [2] but is now known to have a worldwide distribution and is endemic in many areas of Africa [3], Australia [4], North America [5], South America [6,7] and Asia [8,9]. For a number of decades, Vaccinia virus (VACV) was the etiological agent of a similar disease in domestic pigs with distinctive pustular lesions [10].…”