Paw Prints

FERAL AND COMMERCIAL HOG DISEASE CONCERNS

Swine Health Issues Concern Producers and Regulators

According to fable, three little pigs built houses of brick, wood or straw to protect themselves against the wolf.  Swine producers now work with pen design, housing construction and biosecurity measures to protect pigs against another wolf: wild (feral) hogs that can carry and transmit disease.  And, there’s no shortage of the wild pigs in Texas.  Of the nearly 3 million swine in the state, more than two million are wild.

The U.S. Department of Agriculture’s Wildlife Services in Texas submitted samples from nearly 700 wild swine from August 2003 through May 2007.  Test results showed that more than 20 percent, or 142 of 697 pigs had pseudorabies, a highly contagious viral disease that can cause mild flu-like signs in sows and boars, or kill piglets. About 10 percent, or 66 of 676 of the feral hogs were positive for swine brucellosis, a bacterial infection that can cause sows to abort.  Swine brucellosis also may be transmitted from infected pigs to handlers.

The USDA, in its Program Standards for Pseudorabies Eradication, has classified swine based on how well their housing protects against wild hogs.  “Commercial” swine, says the USDA, have the greatest protection and are maintained under high levels of biosecurity  “Transitional” swine live in pens or on farms where it is conceivable that feral swine could burrow under, climb over, or go through fencing to commingle with the domestic pigs.  Captured feral swine also can be included in the “transitional” swine herd.   The USDA’s third classification is for “feral” swine--pigs running free.

Since 2004, all “commercial” swine herds in the U.S. have been officially free of pseudorabies.  USDA regulations allow commercial and transitional swine to move interstate without pseudorabies test requirements.  While individual states may establish their entry requirements, these must meet, and may exceed, the USDA’s Code of Federal Regulation (CFR) standards.

The USDA has not applied the three classifications of pigs in the national swine brucellosis eradication program. Texas is the only state not officially swine brucellosis-free.

To protect against potential disease introduction, the Texas Animal Health Commission (TAHC) requires incoming breeding swine six months and older to be test-negative for swine brucellosis within 30 days prior to entry.   The animals also must be vaccinated within the previous 30 days with a Leptospirosis vaccine containing the Canicola, Hardjo, Icterohaemorrhagiae, Grippotyphosa, and Pomona strains.  The USDA also stipulates that swine moved across any state lines be identified with ear notches, an ear tag or a number tattoo, and travel with a certificate of veterinary inspection issued within the previous 30

days.  The swine must not have been fed waste food or been exposed to hog cholera or pseudorabies, or vaccinated for pseudorabies.

The TAHC allows feral swine to be imported from other states, directly to slaughter, provided the pigs are transported in sealed trucks and accompanied by a VS 1-27 permit (a USDA document that can be issued by a USDA or state animal health official).

Swine Health Problems in Texas

In a recent meeting with the Swine Health Committee of the Texas Pork Producer’s Association, TAHC veterinarians recapped Texas statistics from January 2003 through May 2007.  Forty “transitional” swine operations had been quarantined at one time or another, due to pseudorabies or swine brucellosis infection.  Of the 40 operations, both diseases were detected in nine herds, and two had repeated infection.

A dozen of the 40 operations had definite contact with feral swine, while 14 were reported to have had “possible” contact.  The remaining herd owners said there was no contact with feral swine.  However, the TAHC said feral swine can transmit disease to domestic pigs. When these diseased or exposed mestic swine are moved, they start the disease cycle again. This is referred to as “feral-related” infection.

In the report to the Swine Health Committee, the TAHC “zeroed in” on infection for 2006 and 2007, reviewing with the committee the testing and epidemiology conducted to confirm the source and/or spread of infection.  In 2006, 13 Texas “transitional” herds were found to have pseudorabies. In 2007, six infected herds have been found, as of late July.   Fifteen Texas “transitional” herds had swine brucellosis in 2006, with one detected so far in 2007.

Also troubling is the transmission of swine brucellosis to cattle, which has occurred at least 17 times since January 2006. Swine brucellosis in cattle is not of concern in the cattle brucellosis program, because swine brucellosis is not transmitted from cow to cow.  However, it will cause infected cattle to test positive on brucellosis tests at the livestock market and at the laboratory.   While laboratory confirmation is underway, the cattle herd must be held and tested, creating an inconvenience for the rancher and plenty of concern for the TAHC. If the infection is identified as swine brucellosis, the herd is released, and it’s back to business as usual.

Pseudorabies or swine brucellosis can be detected through “first-point” or livestock marketing testing, required by the TAHC for sows and boars changing hands.  In 2006, blood samples were collected from more than 4,000 swine at the market, and forwarded to the State-Federal Laboratory for testing.  The change of ownership testing for breeding swine six months of age or older also applies to private treaty sales.

Testing of sows and boars slaughtered in Texas accounted for another 2,156 tests.  Feeder pigs are not test-eligible, although they are moved frequently among small herds, and can play a role in disease transmission, reported the TAHC.  When infection is detected, the TAHC tests the swine in the herd of origin.  If infection is confirmed, the herd owner is encouraged to have the swine depopulated.  Federal indemnity funds, at market value, are available to pay the owner for domestic swine, but not for feral hogs.  Prior to restocking, the owner’s pens and facilities must be disinfected, to prevent the reintroduction of disease.

Disease surveillance is also conducted with “high-risk” herds, which include about 325 Texas-permitted waste food feeders, which are tested every two years. Since 2001, the feeding of meat scraps has been prohibited, due to the risk of disease transmission.  Texas’ USDA field staff inspects the waste food feeding operations routinely to ensure that only allowable productsfruit, breads, and vegetablesare provided to the swine.  The TAHC meets with these and other owners of “transitional” swine herds, and has conducted more than 1,400 swine surveys in 2007.  From these, about 50 high-risk herds were identified for testing, and infection was detected in two herds.

The most difficult and time-consuming aspect of disease surveillance and eradication is the epidemiological investigation.  This work involves finding out where, when and how owners obtained or sold swine that my have been infected with or exposed to disease. The investigation will lead to additional herds that must be tested, and if more infection is found, the epidemiological work begins again.  Sometimes, reported the TAHC, the schematic of the epidemiology will begin to look like a giant spider web, as animals are purchased, sold, moved and traded from herd to herd.

Conclusions: Helping Herds Avoid Disease

During the most recent legislative session, the TAHC was provided authority to regulate feral swine for animal health issues.  For several years, the TAHC has approved the placement of the 75 or so TAHC-permitted feral swine holding pens and has allowed the captured wild hogs to go only to slaughter.  Furthermore, rules have been in place requiring the testing of feral swine captured for transport locations other than slaughter, such as a hunting preserve.

To address feral swine health issues, the TAHC will establish a working group with the swine, hunting, and trapping industries to formulate more practical, effective, and enforceable regulations that protect swine production, while also benefiting the hunting industry.

At the same, should new entry and intrastate movement requirements be considered?   Furthermore, the term “transitional” swine may be too broad, because it lumps together high-quality show pig and production farms with all backyard operations and waste food-feeding complexes.  An additional term may be needed for small herds that are not “commercial,” but are well managed and have swine health safeguards.  More than 150 Texas “transitional” herds shipped swine interstate in 2006, and no infection was detected in pre-movement testing of animals.

Other measures to protect swine health?

1.      Keep feral swine OUT.

2.      Improve traceability of domestic swine to help animal health officials conduct thorough and complete epidemiological investigations.

3.      Ensure that swine entering your herd have tested negative for pseudorabies and swine brucellosis.

4.      Keep new additions separate from the rest of the herd for at least 30 days.

5.      Don’t borrow boars, unless they have been tested.

6.      Consider enrolling in the pseudorabies or swine brucellosis certification programs.

          About 70 Texas herds currently are enrolled and have herds tested on a routine basis.

          It’s a good marketing tool, particularly if you sell swine interstate.

7.      If you have sudden widespread illness or unusual death losses in your herd, or see blisters or sores

on your swine, immediately call your private veterinary practitioner and/or the TAHC

at 800-550-8242.