The hog cholera outbreak taught some tough lessons from which the U.S. can learn.
Fifteen months ago, a pork industry's worst nightmare occurred in one of the world's top hog-producing countries. It started when one producer in The Netherlands sustained a 10% death loss in finishing hogs. Lab samples yielded no answers.
Two days later, on Feb. 3, 1997, the producer and his veterinarian sent hogs to slaughter. At the plant, the government veterinarian saw pathological signs of hog cholera. On suspicion of the disease, the veterinarian immediately closed the plant.
Word of the hog cholera outbreak spread like wild fire through the country. And the disease closely followed.
Since then, the hog industry in this tiny country has felt an overwhelming blow from hog cholera's devastation. As of March 1998, 429 farms have broken with the infection. More than 10 million hogs have been destroyed.
Today, the hog cholera outbreaks are nearly contained. Only one new outbreak has occurred since January, but the country is left with the incredible task of cleaning up farms and restocking. They're also left with the job of preventing a future outbreak of hog cholera or other foreign disease.
Other countries like the U.S. and Canada hope to learn from The Netherlands' experience. The possibility of foreign disease outbreaks remains a real threat. What worked and what didn't in this country will be closely studied around the world.
Canadian Help A group of Canadian veterinarians learned firsthand what worked in the battle against hog cholera. When the disease began it's ravage on the Dutch, 34 Canadian veterinarians went to help. They were among 300 people who worked on the outbreak at its peak.
Dorothy Geale, DVM, with the Canadian Foreign Animal Diseases staff was among those who went overseas. Not only was she and the other Canadians there to help, they were also there to learn. Geale related the hog cholera incident to delegates at the Pork Industry Forum held recently in Reno, NV.
Hog cholera is also known as classical swine fever. Geale reports the virus is present in all excretions of the pig and remains relatively resistant to cleaning and disinfectants.
Canada eradicated the disease in 1963 and the U.S. in 1976. Mexico, however, has not eradicated the disease but has an active campaign for it. And feral swine in the European Union still harbor it.
The hog cholera virus infecting The Netherlands is genetically identical to one in Germany. "It is quite likely the virus came into The Netherlands on transport trucks that had not been properly cleaned and disinfected coming across the border," Geale says.
In fact, the virus sat undetected in the country six weeks before the first reported outbreak. But after that first outbreak, 10 more were reported within the first week in the southern part of the country, Geale adds.
Then, several situations worked against the Dutch in their early containment of the disease. The first occurred on the night of Feb. 3, 1997, the day before the country could halt all movement of swine in the area.
Night Of Lights "The night of Feb. 3 is referred to as the night of lights," Geale says. After confirmation of hog cholera, Dutch producers knew hog movement would soon be restricted. They had faced movement control orders before.
"So, many producers moved pigs all that night in anticipation of the stand-still order," Geale says. "They moved the disease across the entire southern part of The Netherlands.
"We imagine that the truckers picking up pigs weren't disinfecting between farms," she continues. "They are picking up pigs from as large an area as they can, especially with the urgency of the situation."
The next situation aiding the spread of hog cholera was the proximity of farms. Geale says most Dutch farms average about 250 sows and generally are located only 300 yd. apart. About 5% of the farms are within 2-6 yd. of each other.
"This virus is not supposed to be spread by aerosol," she says. "But when you have farms that close together and you clean and disinfect with spraying, the Dutch suspect the virus can spread up to 100-200 yd. on particulate matter when airborne."
Because the farms are so close, neighbors also help each other out, meaning movement from farm-to-farm.
About two-thirds of production in the infected area produced nursery pigs. So this means considerable transport usually is involved.
Semen Suspect During the hog cholera outbreaks, the Dutch also discovered semen may spread hog cholera. "This was not known until this outbreak," Geale notes.
Two AI units were involved in the outbreak. One unit located in the hog cholera control area stopped production immediately. The second one located just outside the control area stopped collection and distribution of semen after four months.
The Dutch assessed how the infected farms broke with hog cholera. They determined that 30 farms were most likely infected through semen and AI. "These farms were isolated from other infected premises," Geale says. "The infection had started in the inseminated sows."
However, the Dutch have not proven conclusively that the virus was in the semen, she adds. It could have been contamination associated with semen containers.
Stand-Still Order After the first outbreak, the Dutch put in the stand-still order. This meant no animals or poultry within nearly two miles of the infected farm could move without clinical assessment. This area was called the protection zone.
A surveillance zone of 6.2 miles around the infected farm also was set up for close monitoring. Later during the outbreaks, the Dutch added a 25-mile radius buffer zone around new outbreaks. Herds were clinically assessed, suspect animals tested, and if infected, the herd was destroyed within a day of diagnosis.
The Canadians were needed to help test all the animals in the protection zone within one week of an outbreak. During the stand-still order, producers could not move a thing from the farm, including manure, poultry, etc. After they were cleared, the producers received permits allowing some movement.
The disease peaked last summer with 27 cases/week. Then outbreaks tapered off to only one in March 1998, a year later.
Halting The Spread In retrospect, Geale says it took several components to halt hog cholera's spread through The Netherlands. They were:
* Preemptive Slaughter - Geale says the Dutch learned preemptive slaughter helped control the spread of hog cholera due to the density of hogs. All hogs within .62 miles of an outbreak and not infected were seized and slaughtered at special locations. One site, for example, was a former fertilizer plant.
At the peak of the outbreak, 23,000 hogs were killed in a 24-hour day at the special killing sites. The pigs were handled according to humane guidelines and were electrocuted. The carcasses were sent to rendering.
Infected pigs were not brought to these sites. Instead, they were killed on-site.
The U.S. would have to use a different plan than this, however. Non-infected animals within a control zone can be slaughtered and used for human consumption. "The EU would not tolerate pork from uninfected animals in hog cholera areas to go into the human food chain," Geale says.
* Compensation - "Compensation is probably the most important thing to the producers," Geale says. "Industry and government have to work together to develop a realistic compensation. And they were getting close in The Netherlands."
During the outbreaks, Geale says more and more of the initial cases were reported by producers. This is because the compensation was tied to the number of healthy pigs. Producers only received 50% value for sick pigs. So the earlier they got the veterinarian out to check the pigs when an outbreak was suspected, the fewer animals that got sick. This meant they received more compensation.
* Serological Survey - "The Dutch changed their policy from looking for the disease clinically to also doing serological surveys," she explains. "Every farm herd (in surveillance areas) was sampled at 4-week intervals to see if the disease was coming in and if they could detect it by the presence of antibodies or the virus."
* Biosecurity - Biosecurity was crucial at the crisis center where the veterinarians and government officials monitored the outbreaks. Showers, protective clothing, a separate entrance for those returning from farms and even a foodservice in the building cut down on potential disease transmission.
But even more important was biosecurity on the farms.
"There is a biosecurity protocol written," Geale says. "Each producer has to be their own enforcement officer. The majority of farms had a log where you signed in. That's a wonderful reference if you're trying to trace a virus."
* Manpower - It took expertise from the private sector working with government officials to make the system work, Geale says.
An enormous amount of samples and tests had to be conducted. The Dutch pulled in veterinarians, swine specialists, foreign specialists and students to help with the tasks.
"Canada, like the U.S. government, does not have the individual manpower to do this alone," Geale says.
* Communication - "Communicate, communicate, communicate," she adds. "The Dutch had a website dedicated to the outbreaks with premise information and number of animals involved. They had a telephone hotline, weekly updates to the media and industry meetings."
All these factors combined to reduce the spread of hog cholera through the country. Now, it is up to the U.S. and Canada to refine their own plans for facing a similar disease outbreak should it ever happen.
