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prrsv
The porcine reproductive and respiratory syndrome virus (PRRSV) is a disease that affects all pigs (piglets, fattening pigs and sows). The virus causes respiratory diseases in piglets and fattening pigs, however, symptoms occur predominantly at weaning.
Additionally, PRRSV has a negative influence on the performance of the infected (asymptomatic) pigs. In sows, the disease is characterized by fertility disorders, in particular late abortion (premature birth), and an increased number of stillborn and weak born piglets. ‘Healthy’ born piglets will suffer from several problems such as streptococcus outbreaks, respiratory infections and reduced growth.
Consequently, the antibiotic usage is high at infected farms, due to those secondary infections. In acute outbreaks the virus can cause mortality in adults. Since the virus first appeared in North America, 25 years ago, it impacts the pig industry economically.
Variants of PRRSV virus making control difficult
PRRS virus that was isolated in the US, showed small differences with the PRRS virus that was isolated in Europe. Therefore, there is still a distinction in between an "American strain" (Type 2) and a "European strain" (Type 1). In Europe, until now, mostly Type 1 is prevalent, in North America and Asia mostly type 2 is circulating. Within the types there is still a great variation between virulence and pathogenicity. Immunity induced by infection with variant 1 induces a degree of cross-protection against variant 2. The many variants of the PRRS virus makes the control of PRRSV in companies any easier. Two critical points as an example: 1) vaccination does not provide 100% protection, because the field virus may be different from the vaccine virus; 2) purchase of new animals is a significant risk to the farm, because introducing a new variant can be dangerous, even if the herd has built immunity by vaccination or a previous infection with PRRS virus.
Survival of PRRSV
To select the appropriate control measures, it is necessary to know the stability of the virus. The PRRS virus can survive at low temperature. Consequently, a greater spread of the virus is detected in the winter months. At room temperature, the virus can only survive a few hours in the environment. In water and feces, the virus survives at low temperature (4 ° C) for about 10 days. Luckily, the virus is sensitive to the action of soap and disinfectants.
If all of the animals have acquired protective immunity on a company, and there are no new animals introduced, the disease will be under control on that farm.
Control and prevention
In most regions (such as Europe) the virus is endemic, making eradication impossible. Therefore, control of PRRS is very important. Each farm must monitor its PRRS status. Practically, it is an evaluation of possible infected pigs/groups and the spread of the virus within the farm. It is advised to start with the evaluation of PRRS status the piglets and continue with the other groups such as the sows and the fattening pigs. Once the PRRS status is known, a farm specific control program can be developed, including biosecurity measures, adapted vaccination schedule, appropriate gilt and farrowing unit management, controlled purchase of sperm etc. In case of PRRS vaccination of piglets, only 47% of piglets are seroconverting to the vaccine 14 days after vaccination, making the group still very vulnerable for PRRS challenge. Unpublished results show that beta glucan supplementation before vaccination can speed up the seroconversion (75% seroconverted animals after 14 days) and increase (+42%) antibody titers, meaning a better and faster protection of the herd.
It is clear the prevention and control of PRRS is complex and very farm specific. A close partnership between the veterinarian and farm manger is the key to success.
Interested in how health supplements can play a role in PRRS prevention? We created two documents to share our insights. Both documents take a closer look at the role algae beta-glucan can play as a preventive strategy.
