Risk factors associated with small-ruminant lentiviruses in sheepfold buildings

Abstract

Introduction. Small-ruminant lentivirus (SRLV) infection is widespread across Europe. It causes substantial economic losses in sheep breeding. The main route of SRLV infection is through the mother's milk, especially colostrum However, infection can also occur via contact between infected and healthy animals. It should be noted that the mechanisms of contact infection are still relatively poorly understood. The virus can also spread through a flock via an aerogenic mechanism. Objective. Due to the increased risk of SRLV infection in sheep bred in an alcove system, this study sought to define the effect of various selected factors associated with alcove breeding on the frequency of SRLV infection in sheep Materials and method. Risk factors associated with small-ruminant lentivirus (SRLV) infection were analyzed among flocks of sheep in central-eastern Poland. Ninety-eight sheep flocks were selected for detailed investigation and included 6,470 ewes and 15 breeds and lines. Serologic testing of blood samples was used to identify infected animals and evaluate the epidemiologic status of particular flocks. Specific antibodies for Maedi Visna Virus (MVV) were detected via ELISA. Questionnaires were used to gather information concerning risk factors. Results. The study's results indicate that factors associated with environmental conditions under which sheep are kept play a significant role in determining the risk of SRLV infection. Conclusions. Special attention should be focused on airborne contamination associated with the technologies used in sheep breeding. Breeding technologies that limit airborne contamination in farm buildings should be employed. In developing programmes to eliminate SLRV in sheep flocks, improvement of zoohygenic conditions should also be considered.

A Longitudinal Cohort Study of Risk Factors Associated with Small Ruminant Lentivirus Seropositivity in Intensively Reared Dairy Ewes in Greece

“…These findings are consistent with two relevant studies conducted in Greece in the past (reporting a seroprevalence equal to 65.0% and 47.0%) [30,31], which however did not include any information regarding the implemented farming systems. The animals in our study were reared under intensive farming systems, which are known to favour SRLVs transmission due to the close contact of animals and the poor ventilation conditions compared to the extensive farming systems [15,18,[35][36][37][38][39].…”

“…Age has been recognized as a risk factor significantly associated with seropositivity in many studies [4,17,18,37]. This association has been attributed to the late seroconversion of infected animals [40], the establishment of latent infection for a long period after the initial infection of the animals [1], and the increased risk of infection for older animals due to longer exposure to the virus compared to young animals [18].…”

“…Currently, a number of possible risk factors have been identified as being related to SRLVs seropositivity, both at the animal (e.g., age, breed, sex) and farm levels (e.g., intensive farming system, increased flock size, unfavourable housing conditions, breeding stocks trade, etc.) [4,15,[17][18][19][20][21][22][23][24][25][26][27]. In all cases, however, the study design referred to cross-sectional epidemiological studies, including a wide range of farms, breeds, and animals reared under various farming systems.…”

Seropositivity for Maedi-Visna virus in sheep in Porto Acre city - Western Amazon, Brazil

“…The type of breeding has a direct influence on seropositivity rates. Intensive systems increase the possibility of transmission of the pathogen through direct contact, aerosols (29) or even by breastfeeding (10) . In the municipality of Porto Acre, most properties adopt a semi-intensive or extensive management system, with low agglomeration and population density in the farms.…”

“…In addition, the presence of risk factors, such as failures in health management, intercurrent diseases, absence of quarantine, inefficient technical assistance, and, mainly, the lack of investment in the diagnosis of infectious diseases in sheep must also be considered (29,32) , a reality observed in the municipality of Porto Acre. This critical situation determines the introduction of infected animals, as well as the spread and perpetuation of the virus in herds.…”