Caprine arthritis-encephalitis virus in semen of naturally infected bucks

Sodium dodecyl sulfate as a viral inactivator and future perspectives in the control of small ruminant lentiviruses

ABSTRACT Infections by small ruminant lentiviruses (SRLVs) affect goats and sheep causing chronic multisystemic diseases that generate great economic losses. The caprine lentivirus (CLV) and the ovine lentivirus (OLV) present tropism for cells of the monocyte/macrophage lineage, which are directly associated with the main route of transmission through the ingestion of milk and colostrum from infected animals. In this manner, controlling this route is of paramount importance. Currently, researches have investigated the use of chemical additives in milk that can preserve colostrum or milk and inactivate microbiological agents. Among the compounds, sodium dodecyl sulfate (SDS) has been shown to be satisfactory in the chemical inactivation of HIV and CLV in milk, and also as a biocide in goat colostrum.

Small ruminant lentiviruses: genetic variability, tropism and diagnosis

Small ruminant lentiviruses (SRLV) cause a multisystemic chronic disease affecting animal production and welfare. SRLV infections are spread across the world with the exception of Iceland. Success in controlling SRLV spread depends largely on the use of appropriate diagnostic tools, but the existence of a high genetic/antigenic variability among these viruses, the fluctuant levels of antibody against them and the low viral loads found in infected individuals hamper the diagnostic efficacy. SRLV have a marked in vivo tropism towards the monocyte/macrophage lineage and attempts have been made to identify the genome regions involved in tropism, with two main candidates, the LTR and env gene, since LTR contains primer binding sites for viral replication and the env-encoded protein (SU ENV), which mediates the binding of the virus to the host’s cell and has hypervariable regions to escape the humoral immune response. Once inside the host cell, innate immunity may interfere with SRLV replication, but the virus develops counteraction mechanisms to escape, multiply and survive, creating a quasi-species and undergoing compartmentalization events. So far, the mechanisms of organ tropism involved in the development of different disease forms (neurological, arthritic, pulmonary and mammary) are unknown, but different alternatives are proposed. This is an overview of the current state of knowledge on SRLV genetic variability and its implications in tropism as well as in the development of alternative diagnostic assays.

DETECÇÃO DO VÍRUS DA ARTRITE ENCEFALITE CAPRINA NO SÊMEN ATRAVÉS DAS TÉCNICAS DE PCR E NESTED-PCR

RESUMO A Artrite Encefalite Caprina é uma enfermidade de caráter multissistêmico afetando animais de qualquer idade e sexo; causado por um Lentivirus caprino pertencente ao grupo de Lentivirus de Pequenos Ruminantes. Os sintomas conhecidos são leucoencefalomielite, pneumonia intersticial crônica, artrite e mastite intersticial endurativa. Foi descrito que machos soropositivos apresentavam sêmen infectado pelo Lentivirus e processo inflamatório gradual do testículo. A detecção em amostras de sêmen pelas técnicas de PCR e nested-PCR são caracterizadas como métodos de altas especificidade e sensibilidade provendo resultados rápidos. O objetivo do estudo foi detectar, por meio da técnica molecular de PCR e nested-PCR, a presença de DNA pró-viral do Lentivirus caprino em amostras de sêmen de reprodutores criados no Estado de São Paulo. Das 17 amostras, cinco (29,4%) apresentaram a detecção do vírus provando que há a presença de partículas virais no sêmen dos caprinos reprodutores soropositivos a Atrite Encefalite Caprina estudados.

Maedi in slaughtered sheep: a pathology and polymerase chain reaction study in southwestern Iran

Maedi-visna (MV) is an important slow viral disease of sheep leading to a progressive lymphoproliferative disease. It affects multiple organs primarily the lungs, where it causes interstitial pneumonia (maedi). In this study, the lungs of 1,000 sheep carcasses were grossly inspected and those suspected to have maedi were studied at histopathological and molecular levels. A polymerase chain reaction (PCR) technique that amplified a 291-base pair DNA in the long terminal repeat (LTR) sequence of MV provirus was conducted on all the 50 suspected lungs together with 10 normal appearing lungs as controls. Amplicons of the expected size were detected in 11 (n=11/50) suspected sheep, and one of the 10 control sheep. Histopathologic study of the pulmonary lesions of all 11 (n=11/11) positive sheep showed MV lesions, including hyperplasia of the perivascular and peribronchiolar lymphoid cells, interstitial lymphoplasmacytic infiltration and smooth muscle hyperplasia and the histopathologic findings were correlated with PCR results. In contrast, the tissue sections of control animals were almost normal at histopathological level; however, PCR technique demonstrated that one of them was affected by maedi. This study showed that the LTR-PCR had high specificity and sensitivity in diagnosis of this viral infection. This study is the first to evaluate the prevalence of MV virus infection in sheep in Iran.

AVALIAÇÃO IMUNOHISTOQUÍMICA E ULTRAESTRUTURAL DE GAMETAS E EMBRIÕES CAPRINOS INFECTADOS COM O CAEV

RESUMO O objetivo do presente estudo foi determinar a susceptibilidade dos folículos ovarianos, espermatozoides e embriões caprinos ao Vírus da Artrite Encefalite Caprina (CAEV). Para isto, foram analisados espermatozoides e folículos ovarianos pelas técnicas de imunohistoquímica e microscopia eletrônica de transmissão, antes e após protocolos de infecção in vitro com o CAEV. Foram submetidos à análise ultraestrutural, embriões caprinos produzidos in vivo, oriundos de cabras negativas e positivas para o CAEV. Nas amostras seminais, provenientes de animais tanto com infecção natural quanto dos artificialmente infectados, foi observada imunomarcação positiva dos espermatozoides, assim como alterações degenerativas na sua análise ultraestrutural. Já nas amostras de tecido ovariano, a imunomarcação foi mais discreta e identificada na região do estroma. No tocante à análise ultraestrutural, folículos e embriões se apresentaram íntegros. De acordo com esses resultados, pode-se concluir que os espermatozoides caprinos apresentaramse infectados, assinalando a susceptibilidade dessas células ao vírus, bem como a potencialidade do CAEV ser carreado ao cerne do oócito, originando embriões infectados.

Seroprevalence of caprine arthritis-encephalitis virus in goats in the Cariri region, Paraiba state, Brazil

The seroprevalence of caprine arthritis-encephalitis virus (CAEV) in the Cariri Region of Paraíba State, Brazil, was determined in 60 goat herds using the agar gel immunodiffusion test. The overall seroprevalence was 8.2%, with seropositivity in 21/60 (35%) herds and 13/15 (86.6%) municipalities. Bucks had a significantly higher frequency of infection (28.3%) than does (5.9%), and bucks that originated in other states had a significantly higher frequency of infection (76.5%) than those from Paraíba State (9.3%).

Overview of herd and CAEV status in dwarf goats in South Tyrol, Italy

The analysis of the electronic data processing proved that 323 dwarf goats older than 6 months from 165 farms were kept in 63 of the 116 communes of South Tyrol. The number of dwarf goats maintained ranged from 1 to 19 animals, the average farm size revealed to be of 2 dwarf goats/farm. 47 animals were aged between 6 months and 1 year (AG1), 97 were between 1 - 2 years of age (AG2) and 179 were aged older than 2 years (AG3). The mean age amounted to 3.8 years, the age limit being 10 years. 235 animals were female and 88 animals were male (sex ratio 2.7:1). 187 animals (57.9%) were born between November and April and 136 animals (42.1%) were born between May and October. 13 animals (4.0%) proved to possess antibodies against CAEV in a serological examination performed with ELISA. The herd seroprevalence was 6.1% (10 positive farms). The seropositivity did not vary significantly in the different age groups (AG1: 4.3%; AG2: 4.1%; AG3: 3.9%). The seroprevalence of animals born outdoors between November and April (5.9%) did not differ significantly from those born indoors between May and October (1.5%). The seroprevalence of the female animals (3.4%) did not vary significantly from that of the male goats (5.7%). The low seroprevalence ascertained in the dwarf goats in South Tyrol is due to the non-existing milk production, the marginal contact among each other as well as the sparse animal trade. This study should prompt adequate means of control to be established, so that the introduction of positive animals can be prevented. An eradication programme would be advisable, due to the low disease prevalence and its chances to be successfully implemented.

Development of a semi-nested PCR using degenerate primers for the generic detection of small ruminant lentivirus proviral DNA

A PCR assay was developed for the reliable detection of small ruminant lentivirus (SRLV) proviral DNA. The method involved the use of degenerate deoxyinosine-substituted primers and a second semi-nested PCR step that increased the polyvalency and sensitivity of the detection, respectively. Primers were designed from the pol gene conserved motifs of 85 SRLV isolates and were evaluated using different SRLV isolates together with Maedi-Visna virus (MVV) and caprine arthritis-encephalitis virus (CAEV) reference strains. The method successfully detected SRLV proviral DNA in total DNA extracts originating from whole blood samples, separated peripheral blood mononuclear cells (PBMCs) and tissue cultures. The semi-nested PCR was compared with the agar gel immunodiffusion test and proved to be highly sensitive, specific and capable of detecting many SRLV variants in infected or suspect animals. Therefore, it would be useful in the diagnosis of natural SRLV infections, in eradication programs and epidemiological studies. Whole blood samples can be used directly, thus alleviating the need for PBMC separation, and thereby enables a simple, fast and cost-effective analysis of a large number of samples.

ARTRITE ENCEFALITE CAPRINA EM CABRITOS DE REBANHOS COM PROGRAMA DE CONTROLE NO ESTADO DO CEARÁ

RESUMO A artrite encefalite caprina (CAE) doença vírica comum em cabras leiteiras. A introdução de animais infectados no rebanho é uma das formas de disseminação mais importantes, especialmente, pela dificuldade de diagnóstico nos estágios iniciais. Objetivou-se verificar o risco de disseminação da CAE através da comercialização de animais jovens soronegativos. Foram utilizados 46 animais da raça Saanen de aproximadamente 1 ano de idade, sendo todos filhos ou netos de animais soropositivos para CAE. Estes animais foram acompanhados clinicamente por 1 ano, sendo submetidos a 2 testes de imunodifusão em Gel de Agarose (IDGA), para a detecção de anticorpos anti-caev, feitos com intervalo de 6 meses. Ao final deste período os mesmos foram submetidos ao teste de Reação em Cadeia de Polimerase-Nested (PCR-Nested) para a detecção do DNA proviral em monócitos. Nos testes sorológicos apenas um animal apresentou resultado positivo no segundo exame, enquanto que no PCR-nested 35 mostraram-se positivos (76,08 %). Pode-se concluir que a aquisição de animais jovens, oriundos de propriedades com histórico de CAE, representa um alto risco na disseminação desta enfermidade, especialmente, quando se utiliza o teste de IDGA como único método de diagnóstico da infecção no momento da aquisição destes animais.

Diagnostic tests for small ruminant lentiviruses

Maedi visna virus and caprine arthritis encephalitis virus are closely related retroviruses that cause chronic inflammatory disease in small ruminants. The infections are characterised by insidious onset and slow progression. Diagnosis of infection is usually by serological testing. A variety of assays are available for this purpose, though the relative sensitivity and specificity of these assays has not been compared systematically. Here we review recent developments in laboratory diagnostic methods and their use in field diagnosis. The results suggest that a combination of ELISA and PCR might afford optimal detection of SRLV infection.

Lentivírus de pequenos ruminantes (CAEV e Maedi-Visna): revisão e perspectivas

Os lentivírus de pequenos ruminantes (SRLV), cujos protótipos são os vírus da Artrite-Encefalite Caprina (CAEV) e Maedi-Visna, são patógenos amplamente distribuidos, os quais causam doenças degenerativas progressivas lentas em caprinos e ovinos, determinando importantes perdas econômicas. Estes vírus causam infecções persistentes com período de incubação longo e causam inflamatórias e degenerativas. As lesões são induzidas em tecidos específicos do hospedeiro como articulações, pulmões, CNS e glandulas mamárias devido à replicação viral em células da linhagem monocítico-fagocitária que são as principais células-alvo. A infecção ocorre principalmente durante os primeiros meses de vida, através da ingestão de vírus no leite ou colostro de cabras ou ovelhas infectadas. A indução da resposta imunológica é variável e não protege contra a infecção. O diagnóstico é baseado primariamente na detecção de anticorpos para SRLV, geralmente por imunodifusão em gel de agar (AGID) e enzyme linked immunosorbent assay (ELISA). O diagnóstico e separação ou descarte dos animais soropositivos associado ao uso de certas práticas de manejo, especialmente das crias, são os principais meios implementados para prevenir a disseminação de SRLV, uma vez que ainda não existe vacina contra o vírus. As estratégias adotadas pelos SRLV para enfrentar o sistema imune dificultam o diagnóstico da infecção, controle ou prevenção da disseminação de SRLV. Esta revisão apresenta alguns aspectos das lentivíroses de pequenos ruminantes baseadas em estudos filogenéticos de amostras isoladas, aspectos clínicos e imunopatológicos.