Several steps have been taken in the past year to clear porcine circovirus-associated disease (PCVAD) from Kansas herds, all with limited success.
Swine veterinarians Steve Henry and Lisa Tokach have virtually pulled out all the stops in a crusade to lessen PCVAD's strong grip on swine herds in their Kansas practice.
The typical treatment and management schemes normally used to thwart swine disease have yielded less than sterling results.
The veterinary team reported the only thing that has truly worked (at the time of their presentation at the Leman Swine Conference in September, has been the limited use of vaccines available for trial implementation.
Positive results have been seen in several groups of finishers vaccinated at 4 weeks of age. In one vaccinated group, death loss was virtually eliminated all the way through the nursery and finisher phases. In other groups in that same trial, the mortality of vaccinates vs. non-vaccinates was approximately 80% less.
In two groups similarly vaccinated, finishing death loss due to PCVAD has been just under 1% so far. The trial was about halfway through finishing when the report was given.
What's needed now is the approval of more PCVAD vaccines, plus a ready supply of vaccine for U.S. pork producers severely impacted by porcine circovirus type 2 (PCV2), stresses Henry.
Encouraging early results reported by many veterinarians in limited vaccine trials provide optimism. But biologics companies and regulatory agencies need to work together to speed vaccine approvals, he urges.
Producer Frustration Builds
There's no doubt that producer frustration has grown since many Kansas producers saw a dramatic increase in herd mortality starting in the fall of 2005.
Henry says problems typically start 4-5 weeks after placement in the finisher, when pigs are 13-15 weeks old.
In many cases in Kansas, finisher mortality runs 10-20%. Losses decline after the disease runs its course over 6-7 weeks. Deaths and culls can affect 30% of a finisher pig flow, he explains.
High mortality rates are very common with PCVAD, but are not predictable from barn to barn or flow to flow, points out Henry.
Herds with and without porcine reproductive and respiratory syndrome (PRRS) both seem at risk, he says. But co-factors such as PRRS, Mycoplasmal pneumonia and swine influenza virus certainly elevate mortality in porcine circovirus type 2-infected pigs.
Differences in the type of production system and flow, genetic source, semen supply and biosecurity measures all appear to have little impact on whether a herd will experience an outbreak of PCVAD, the Kansas veterinarians agree.
Unique Clinical Signs
Observed clinical signs of PCVAD appear to be somewhat different in Kansas from reports in other states, says Henry. Almost all affected herds have dermatological problems associated with PCV2, with numerous skin lesions in some but not all pigs.
PCV2-affected pigs appear very distressed, lethargic and depressed. Meanwhile, penmates and other pigs in the barn often appear completely normal, achieving expected feed consumption and growth.
Adult animals in breeding herds and nursery pigs of affected farms have not shown recognizable signs of disease that can be ascribed to PCV2 by physical or laboratory examination, he notes.
Henry's list of the 10 most common, detectable signs of PCVAD in individual animals includes:
Growth stops, wasting and dehydration start as a result of sharply reduced feed intake. “Many of these pigs will stand by the feeder and look at the feed but they won't eat.”
Gross enlargement of many major lymph nodes.
Pallor of the skin and indication of oxygen depletion, marked by a bluish discoloration along the rear flanks and margins of the ears.
Respiratory distress with open-mouth breathing after activity, but without a cough in most instances.
Skin lesions, with the most dramatic and common being porcine dermatitis and nephropathy syndrome; about 30% of fatalities tracked had skin lesions.
Nervous condition with noticeable tremors in the rear legs, ranging from subtle signs of weakness to an inability to stand on the rear limbs and dragging the legs when attempting to move. This is observed in a lesser proportion of pigs during PCV2 infections.
Prostration and rapid progression to death.
Pigs avoid exercise, and after even mild effort will immediately drop to a prone position and be reluctant to rise.
Enteritis with pasty diarrhea containing undigested grain.
Ear tip necrosis or damage in affected animals and unaffected animals in some cases.
Attacking the Problem
Henry and Tokach praised the committed efforts of researchers at Kansas State University and Iowa State University in helping define PCVAD pathologically.
A $48,000 grant from the National Pork Board has helped characterize the affliction in Kansas herds.
In addition, producers from the Kansas Swine Alliance committed $32,000, or 50 cents/pig marketed, toward efforts to define and research the issue. “The power of producer commitment to solving emerging problems cannot be overestimated — these producers made a huge difference in progress on this disease,” says Henry.
In their efforts to slow the progression of PCVAD, Henry and Tokach, his swine practice partner at the Abilene Animal Hospital in Abilene, KS, have tried feed and water medications, as well as individual pig therapies with a wide variety of antibiotics and anti-inflammatories — all without discernable value, in their estimation.
Sorting pigs into hospital pens at the first signs of disease and intensifying therapy were both attempted, but these efforts provided no measurable benefit.
That led them to develop the following guidelines:
Provide comfort and reduce stress.
Stop use of injectable therapeutic interventions because of the lack of efficacy, stress of handling pigs and economic cost of using antibiotics.
Understand that the lymphoid damage seen in pigs makes recovery very unlikely, and that disease signs can vary widely.
Identify affected pigs early and euthanize if suffering, or move to a “hospice” pen and reevaluate status; nearly all affected pigs will die or must be euthanized.
Focus on environmental management — comfort, hygiene and sanitation — especially in preparing a previously affected facility for the next group of animals. While PCVAD is a very difficult virus to kill in the environment, producers report that cleaning and disinfecting between groups appears the most effective tool they have utilized.
Cirovirus Vaccine Approved
Boehringer Ingelheim Vetmedica (BIVI), Inc. received word in mid-October that its new vaccine for porcine circovirus type 2 (PCV2) has been approved by the U.S. Department of Agriculture for use in swine.
BIVI's vaccine is called Ingelvac CircoFLEX. It is a single dose, 1-ml. vaccine to be injected intramuscularly into pigs as young as 3 weeks of age, according to Klaas Okkinga, company marketing manager for swine.
The vaccine provides active immunity that will protect growing pigs during the age period when PCV2 typically strikes (late nursery and grow-finish phases).
Company field trials have shown that vaccinating commercial pigs around 3 weeks of age helps producers more effectively manage porcine circovirus-associated disease, says Okkinga.
Ingelvac CircoFLEX carries a 21-day withdrawal period prior to marketing to ensure an adequate margin of food safety.
In extensive field safety studies, the PCV2 vaccine was shown to be very safe, and no elevated systemic and/or injection site tissue reactions were reported, says Okkinga.
He projects that the vaccine will become widely available to the industry in the first quarter of 2007.
For more information, contact BIVI at (800) 325-9167 or visit www.bi-vetmedica.com .