The Pig Site Backroom
It is very interesting that in over half of the farms with PMWS, PDNS problems are also observed. In some herds with severe PDNS outbreaks after PMWS problems, the farmers have informed us that after changing the boars the problems decreased. Given that in PMWS/PDNS affected pigs Circovirus 2 virus can be found in the lymph nodes in very high titers, while in the non-affected pigs in the same group low virus levels are found, speculation is made as to how the immune system of the affected piglets can be disturbed in such a special way.
The influences of the different known factors are restricted to the laboratory tests that are available at the Diagnostic Centers. Combinations of infectious agents in conjunction with stress, housing, feeding and management factors and possibly genetic factors are fields that need to be investigated further.
Vaccinations in sows and pigs against all factors that are available and or tested and showed to be of importance on the farms are carried out on a more intensive schedule as for example vaccinations against PRRS, Mycoplasma hyopneumoniae, Parvovirus and Influenza. No absolute successful strategies are described but a reduction of the mortality or a better treatment result can often be reached with more or less success.
Vaccination against PRRS of the sow herd and piglets on an intensive and strict schedule i.e. sow herds 3 or 4 times per year and the piglets before weaning, did improve the problems in some of the herds. The vaccinations against Parvovirus, Influenza and autovaccines against other diseases, for instance Streptococcus suis, Haemophilus parasuis and Bordetella also helped. But still these vaccinations cannot always solve the problem completely. Investigations are on going to find out more and perhaps identify specific triggers such as other viruses and bacteria.
To handle the increased bacterial infections in piglets affected with the disease, medications in different combinations are used based on the trial and error experiences of vets and herd owners.
Because most of the time only the severely diseased pigs need medication and mostly individual treatments for weeks, it is worthwhile to select these pigs and put them in pens together.
The herd immune status is improved and stabilized by using materials of diseased pigs i.e. faeces or tissues are used to infect and immunize the sows, boars and gilts by oral or intradermal methods. The application of serum from recovered fattening pigs injected into weaned piglets of the same herd in a preventive manner, sometimes results in strong improvements. On other farms, the results of such treatments remain poor.
We have not reached the final solution yet and therefore we still need to improve the medication schemes and optimize housing, climate, stock density, feeding and water supplies, trying to keep the losses caused by PMWS/PDNS as low as possible as well as the period of severe losses as short as possible.
M.F. de Jong ? Animal Health Services Deventer - May 2001