Porcine Circovirus Type-2 in Asia
Last week we discussed measures being taken in Europe for treatment and control of porcine circovirus type-2 (PCV-2). This week we will consider the impact of the disease in Asia as it relates to postweaning multi-systemic wasting syndrome (PMWS).
According to Han Soo Joo, DVM, a member of the Swine Group at the University of Minnesota, severe clinical losses due to PMWS were first observed in the Guangdong province of China in 2001, where swine production is intensive and large pig companies are located.
"Breeding farms first experienced PMWS, and the syndrome spread to the multipliers and commercial farms," notes Joo. "Clinical signs on affected farms were usually observed in grow-finish barns in the initial stage and extended to the nurseries with high mortality. Nursery pigs as young as 3 weeks old were affected during the peak period.
"In South Korea, PMWS or PCV-2 associated diseases have been a major problem throughout the country from about 2001," he continues. "Nursery pig mortality ranging from 10% to 30% was common."
Problems with PMWS related diseases were similar in Thailand, though the disease appears not to have had an impact in the Philippines, where health levels in breeding farms are relatively high, reports Joo.
As in other countries, transmission of the causative agent seems to occur mainly via introduction of replacement gilts from infected breeding farms.
"Careful consideration should be given to semen, since excretion of PCV-2 via semen has been reported," states Joo. "Contaminated feeds can also be a significant source of infection. Of ingredients in the feed, porcine plasma should be considered a risk, and PCV-2 may not be killed during the spray-dry process of the plasma because of its heat resistance. Elimination of the virus from contaminated environments would also be difficult."
Joo stresses the importance of all-in, all-out production, particularly in the nursery phase, to control the disease and reduce virus transmission. In addition, extensive cleaning and disinfection of nurseries is necessary.
"It is also recommended to use two different disinfectants for nursery cleaning, although certain disinfectants were found to be more effective for PCV-2," says Joo. In addition, he says South Korea has access to nutritional supplements that contain high energy/protein, electrolytes, anti-diarrhea drugs, and substances for better digestibility to lower fever or improve the immune system. "Cooked rice powder has been used as the major energy supplement, and egg yolk antibody to PCV-2 has been produced and added in some products."
While data for evaluating these products under controlled experiments are not yet available, Joo notes that leading veterinarians and producers have made good comments about some of the products.
As reported last week, co-infection with other diseases like porcine reproductive and respiratory syndrome (PRRS) virus, porcine parvovirus and other bacterial pathogens have been found to increase the severity of clinical signs and mortality in PMWS farms.
"To reduce mortality, M. hyopneumonia and/or PRRS vaccine has been strategically used for pigs before weaning," states Joo. However, the disease actually seemed to show increased severity of clinical signs when too many vaccines were administered, he says. Some veterinarians have suggested removing unnecessary vaccines or avoiding vaccination of pigs during the early nursery period.
Joo says that on some Asian farms, an autogenous tissue extract vaccine was developed for the prevention of PMWS. Pigs with early clinical signs were sacrificed and affected tissues (lung, spleen, lymph nodes) were collected, he reports. "Although experimental data using the tissue vaccine are not available, an obvious benefit has been observed on PMWS farms and the farm veterinarian reported the continuous use of tissue vaccine during the last three years," notes Joo.
Farms.com Director of Communications, Farms.com
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