Better Pork - October 2003Swine pox is alive and well
Though not rampant, this virus carried and transmitted by the pig louse is still present, as hog farmers in Manitoba and Saskatchewan recently found outby S. ERNEST SANFORD
SARS, BSE (Bovine Spongiform Encephalopathy or mad cow disease) and monkey pox have flooded the news over the spring and summer months.Monkey pox was a total unexpected surprise. It was initially contracted by rodents (Gambian rats) from monkeys in pet stores, then passed to prairie dogs (another type of rodent) and finally to humans in the U.S. Midwest (Wisconsin and Iowa) who had bought prairie dogs as pets from pet stores. Prairie dogs, considered a summer pest throughout the prairies because of their propensity to eat and destroy crops, have apparently become a fad pet in some urban and semi-urban areas of the Midwest.
This all got me thinking about swine pox, which used to be quite common when I started out as a neophyte pathologist in the diagnostic lab system in Ontario 30 years ago. For several years now, I have harboured the vague notion that swine pox no longer occurs in present-day swine operations. Not so! I did a little investigating and found that swine pox is alive and well -- not rampant, but definitely still around.
The pig louse serves as a mechanical vector and is the primary means of transmission of the swine pox virus. The pox lesions are typically distributed along the ventral portion of the pig corresponding to the exact locations normally inhabited by the pig louse. Biting flies and mosquitoes are also likely suspects in transmission of the pox virus within a herd. When transmission occurs via these insects, the pox lesions are distributed on the backs and sides of affected pigs.
Pox lesions start as multiple small reddened areas on the skin, then progress through to a raised fluid-filled vesicle (blister) and finally a pus-filled mass that eventually crusts or scabs over. Bacteria can then infect these skin lesions, causing secondary bacterial dermatitis that worsens and prolongs the skin infection.
One of the more intriguing and less commonly known features of swine pox is that, when the virus infects a pregnant sow, the infection can cross the placenta and be transmitted to the fetus in the uterus, causing pigs to be born with pox lesions on various parts of the skin. Because of the compartmentalization of the pig's placenta, one or more pigs in a litter may be affected at birth and, on rare occasions, the entire litter may be affected. This condition is called congenital swine pox. In fact, the majority of current cases appear to be congenital swine pox rather than the more conventional forms of yesteryear.
I did a quick check of diagnostic labs across Canada to see if swine pox is still being seen on a regular basis and my suspicions were confirmed that it is much less frequent than before. The common pig louse is so rare today that I have to go back more than a couple of decades to pinpoint when last I saw lice on pigs.
However, a mini-rash of cases has occurred in Manitoba and Saskatchewan in recent months. Even more fascinating is that a large percentage of the few cases seen these days are usually congenital swine pox. This would indicate that the virus is still around and is able occasionally to infect a naïve sow.
Swine pox usually occurs in an outbreak manner within a herd and is relatively easily diagnosed by the appearance of the typical pox lesions on the skin of the pig. Histology (tissue study) can be used to confirm the diagnosis and might be necessary because we now have a whole generation which has seen swine pox very infrequently and hence may not be able to diagnose it with confidence on its clinical appearance only. In addition, it is necessary to differentiate swine pox from other conditions that resemble it, such as like insect bites (mosquitoes and biting flies) or hypersensitivity reactions to mange mite infestation.
Because of the recent outbreaks of monkey pox in humans handling prairie dogs in the U.S. Midwest, the question may arise whether humans can contract swine pox by handling pox-infected pigs.
The answer is an emphatic "No!" The swine pox virus infects pigs and pigs only. Other mammals, birds or humans are not affected. BP
S. Ernest Sanford, DVM, Dip. Path., Diplomate ACVP, is a swine specialist with Boehringer Ingelheim Vetmedica (Canada) Ltd. in Burlington.
© copyright 2003 AgMedia Inc..
back Shelterbelts can help reduce odours, so get out there and plant some trees!
Shelterbelts create turbulence at the surface of the terrain that intercepts and disrupts odour plumes, helping to push them into the lower atmosphere. Result: a significant reduction in downwind odour
by Sam Bradshaw
As farmers we are sometimes lulled into complacency by our beautiful surroundings. Often, it requires a trip to other parts of the country for us to realize just what a wonderful place we live in. Trees make up a large part of this beauty.There are many reasons to plant trees on our properties:
To examine the effects of windbreaks on odour mitigation, Ontario Pork is embarking on a research project with the University of Guelph's Arkell Swine Research Facility. This research will try to demonstrate how trees can reduce odour downwind. We will try different spacing, varieties and fertilization applications using hog manure, and also various watering techniques.
- Our property value increases.
- Trees can reduce snow buildup if strategically placed.
- Trees can help buildings blend into the landscape.
- They can disperse and reduce the impact of odours on neighbours.
- Tree buffers can trap and use nutrients.
- They improve working conditions for people and can reduce stress on livestock.
Working with Tracy Ryan and Jason Culp from the Grand River Conservation Authority, Todd Leuty, the tree specialist with the Ministry of Agriculture and Food, and Roger Shantz, farm manager at Arkell, we hope to generate answers to outstanding questions about the effect trees can have on odour.
When dealing with odour, the location where the odour develops is very important. There are three primary sources of odour in confined animal production: the animal confinement buildings, manure storage facilities and land application (Swine Odors Task Force, 1995, University of North Carolina).
In 1986, D. G. Hardwick (1986) counted the number of agricultural premises in the United Kingdom that were causing justifiable odour complaints and found that among 1,820 pig, cattle and poultry farms, 46 per cent of the complaints were associated with manure spreading, 25 per cent with building odours and 19 per cent with manure storage.
According to an article by John Tyndall and Joe Colletti of Iowa State University's Forestry Department, entitled "Air Quality and Shelterbelts: Odour Mitigation and Livestock Production - A Literature Review," there is compelling evidence that shelterbelts will work very well within an agricultural landscape to provide odour control. Because most agricultural odours originate near the ground and the tendency of the plume is to travel along the ground, shelterbelts of even modest heights (20-30 feet) may be ideal for plume interception and disruption. Also, depending on the shelterbelt design and species used, they can provide year-round interception.
There are four primary ways that shelterbelts can improve livestock odours:
Shelterbelts create turbulence at the surface of the terrain that intercepts and disrupts odour plumes traveling in laminar flow, helping to push the plume into the lower atmosphere and facilitating dilution.
- Dilution of gas concentrations of odour into the lower atmosphere.
- Encouraging dust and other aerosol deposition by reducing wind speeds.
- Physical interception of dust and other aerosols.
- By way of acting as a sink for the chemical constituents of odour.
Lowering wind speeds over manure storages can reduce convection of odorous compounds from the surface and allow for slower release of the odor plume, which also helps dilution.
How does this work? Shelterbelts present an obstacle to the wind, deflecting and lifting air streams (odour plumes) upward into the lower atmosphere. The lifting aspect will begin at some distance on the windward side, typically a distance equal to two to five times the height (referred to as 2 -5 H) of the shelterbelt.
In research conducted in 1988, K.G. McNaughton further notes that, as the air streams top the shelterbelt, the stream is redirected, compressed and air speeds increase.
It is important to note that, as porosity of the shelterbelt decreases (<50 per cent), the greater the turbulence created in the turbulent zone. It is in this zone, depending upon the height of the shelterbelt, that much of the dilution of the odour plume can take place.
At a minimum, two rows of trees or shrubs should be used. Wedge-shaped shelterbelts facing the prevailing winds often create more turbulence and push air streams higher into the lower atmosphere. Because height is of particular importance, fast-growing species should be used.
Depending on space available, a simple three-row shelterbelt could be used with a fast-growing deciduous species, such as a poplar variety, planted on the leeward side of the windbreak. A slower-growing species in the middle and a shrub species to windward would create a wedge shape. Though they have a tendency to be somewhat short-lived (often 30-40 years), faster-growing species have the advantage of serving as nurse trees for the other rows, which could be made up of slower, longer-lived species.
Modelling the effects of tall barriers around manure lagoons suggests reductions in downwind malodorous lagoon emissions of 26 to 92 per cent. Wind tunnel modelling of a three-row shelterbelt system has given reductions of 35 to 56 per cent in the downwind mass transport of odorous particulates (dust and aerosols). In general, the horizontal extent of wind protection is proportional to the shelterbelt's height. Shelterbelt porosity is perhaps the most important variable. Shelterbelts with a porosity or density of 40 to 60 per cent provide the greatest reduction in wind speed over the greatest distance.
Measured reductions in wind speed on the windward side of shelterbelts have been recorded at 2 to 5 H of the shelterbelt. Measured reductions in wind speed to the lee (downwind) of a shelterbelt have been varied, with some being recorded as far as 50H of the shelterbelt, although wind speed reductions to about 30H are more typical. At about 8H, wind speeds can be about 25-50 per cent of open field wind velocity.
From about 10H to 20H, wind speed can range from 50-80 per cent that of open-field wind velocity. Porosity can be manipulated by spacing as well as by the species used in the shelterbelt. Shelterbelts of deciduous trees have a tendency to be more open, close to the ground, whereas conifer belts typically have branch cover close to the ground.
A study from 1984 asserts that a forest cleans the air of microparticles of all sizes twenty times better than barren land.
Leaves with complex shapes and large circumferences collect particles most efficiently, suggesting that conifers may trap particles more effectively than deciduous species.
In a paper published in 1994, R. J. Smith noted that leaves with complex shapes and large circumference-to-area ratios collect particles most efficiently, indicating that conifers may be more effective particle traps than deciduous species and also because they are "in leaf" throughout the year.
Volatile Organic Compounds (odour producers) have been shown to stick to the cuticle that covers plant leaves and needles and research on this affinity is currently underway.
Micro-organisms dominate the surface of plants. These organisms take up and hold volatile organic compounds and provide additional surface area for pollution collection. They also have the ability to metabolize and break down these compounds.
Local conservation authorities have a wealth of information on shelterbelts. They will provide technical assistance and help with the planting. Grants covering up to 70 per cent of the cost are available, so what's stopping you? Lets get out and plant some trees! BP
Sam Bradshaw is environmental specialist with Ontario Pork.
© copyright 2003 AgMedia Inc..
back Does proximity to pig farms really reduce residential values?
While some residential property owners near hog operations or concentrated animal feeding operations have succeeded in getting their taxes reduced, it's not so easy to find cases where property values have actually fallenby DON STONEMAN
It's a sensitive issue and one that the swine industry can't seem to shake -- the apparent devaluation of rural residential properties because they are located near to pig farms.Environmental groups opposed to large-scale swine farming use the fear of private property devaluation to arouse local dissent when a pig barn proposal is brought to a neighbourhood. Often, they cite studies from the United States, mostly referring to research done by University of North Carolina economist Ray Palmquist in the 1990s, and they charge that rural properties are devalued as much as 40 per cent when large-scale pig barns are built nearby.
But a closer examination of studies on property devaluation, published as recently as 2001, shows that sometimes there is less than meets the eye. One example is a 1998 study of 75 rural land transactions near Premium Standard's hog operations in Putnam County, Miss. These transactions nearly all concerned bare farmland (no dwellings), which was devalued by $58 an acre on average within 1.5 miles of the barns. A second study by the University of Columbia-Missouri found that land values lost within three miles of a hog intensive livestock operation would amount to approximately $2.68 million US. That sounds like a lot of money, but it works out to $112 an acre.
Similarly, a Sierra Club study of tax adjustments found that at least eight states lowered property taxes for neighbours of concentrated animal feeding operations. Most startling was a tax rollback in Grundy County, Miss., where taxes on some residences were lowered by 30 per cent because they were neighbours of the corporate hog operations of Continental Grain.
Palmquist's research has made itself felt north of the border. The National Farmers Union (NFU) cited this study in 2000 when it sought to prevent the Taiwan Sugar Company from establishing a large hog operation in Alberta's Flagstaff County. The NFU quoted another study by the University of Missouri-Columbia in 1999, which found that an average vacant parcel within three miles of a concentrated animal feeding operation (CAFO) lost about 6.6 per cent of its value, but if a parcel with a house on it was within a tenth of a mile of a CAFO it lost an astounding 88 per cent of its value. A tenth of a mile is 582 feet, close by any standards here in Ontario.
Other research has pointed out that the price-depressing effect of pigs cannot be separated from noise, dust from trucks and a "general decline in the natural beauty of the area" that is associated with development in general. And contrary to Palmquist's research is a 1996 study conducted in southwest Minnesota, which examined housing price sales in two counties and found that proximity to a feedlot actually resulted in higher sales prices. The authors suggested that perhaps the employees wanted to live close to their work.
So what is the situation in Ontario? Better Pork decided to go hunting for homes that had been badly devalued because they were near pig barns and the search, we found, was not easy.
Since the Sierra Club touts Palmquist's research in its opposition to pig barns, we asked its spokesperson to cite some examples of devalued homes and we also spoke to several dozen realtors across western Ontario's hog farming belt.
Maureen Reilly, a Toronto-based spokesperson for the Sierra Club who owns a rural home near Fenelon Falls, east of Toronto, made some inquiries among Hogwatch, an international coalition battling confinement hog farms. She reported no instances of cheap homes for sale, but instead concerns about tax assessments that no longer reflected the value of homes reduced by a nearby pig barn. Hogwatch details are sketchy at best, but one official with Hogwatch Haldimand sought to have taxes reduced on the property because it was near new hog barns and actually had taxes on the home increased.
Better Pork also went looking for homes devalued by their proximity to hog barns and found few realtors who knew of such instances. When this question was put to them, realtors suddenly weren't in the business of selling rural properties, or couldn't think of any hog farms operating in the rural area where they sold homes.
Blyth realtor John Van Eeden-Petersman and Blenheim-based Penny Wilton were two exceptions. Van Eeden-Petersman sold a house near a large hog barn in Huron County's Hullett Township. After extensive renovations, he says the property sold for $120,000, though it should have sold for $185,000. The previous owner had signed off on a farmer's request for an exception to a Minimum Distance Separation rule and "didn't know what he was getting into," Van Eeden-Petersman says.
In Chatham-Kent, Wilton says she periodically runs into rural homeowners wary of pig barns. "Some people don't have any issue with it," she says. "Others do."
In August, she listed a "brand new home" situated mid-way between two pig barns on a dirt road about a kilometer from pavement but with municipal water, which generally increases a home's value. The barns were there first, and the house was built by a farmer "who didn't have an issue with them."
The house is built within the Minimum Distance Separation parameters and, while the dirt road hasn't come up in conversations, the pig barns have. "I just know that I've had comments on it," Wilton says.
One couple that did win a major break on municipal taxes is Julie and Doug Kuik, who live in the Township of Ashfield in Huron County. In November 1999, the provincial Assessment Review Board reduced the assessed value of their severed rural home by 33 per cent because the property is surrounded by land owned and used by a pig operation and the Kuiks have been able to maintain the assessment at the same level since then.
The Kuiks bought their property in 1991 and Acre T Farms Ltd bought the surrounding property in 1996, drawing water from a well beside a bank barn directly behind the Kuik home. Acre T also has a right of way past the Kuik home, which Julie Kuik says is about 1,000 feet from the road. She says the circumstances of her home are exceptional.
The judgment took environmental problems at Acre-T farms into consideration, noting that "the operation of the pig farm has been subject to a number of subsequent operational problems which are still outstanding and may not have been fully corrected."
A report prepared for the Kuiks by Clinton consultant Robert Thomas compared their case to urea formaldehyde foam installed in houses under a government energy conservation program in the 1980s and later found to cause health problems. Thomas argued that the Acre T barn was built to government standards at the time, but that the Kuiks suffered from constant smells from the barn manure venting, excessive flies and concerns that their well would be contaminated or would run dry.
"The subject property appears to be in a worst case scenario," noted the judgment. "The factor may be amended in future years if the operation of the pig facility is improved or other events occur which would affect the marketability of the property."
Another case involving a tax assessment rollback goes back to 1998 in the former township of Howard, now part of the municipality of Chatham-Kent. There, a more conservative tax rollback of 10 per cent was awarded to farm owners Doug Desmond and Joan and Albert Hitchcock and a 15 per cent tax rollback was awarded to rural residential lot owners Janet and John McCredie.
Keith Robbins, director of Communications for Ontario Pork Producers, finds these tax rollbacks somewhat troubling. He worries about perception automatically becoming reality, even if there's no science behind it. "It does have long-term rippling effects."
Monkton pork producer Larry Skinner, chairman of Ontario Pork, expresses surprise that there have been instances where taxes were reduced on properties adjacent to pig barns in Ontario.
He acknowledges that the Ashfield case was extraordinary. "I can see it in those circumstances, particularly the well and the right of way access. Obviously it is affecting their way of life." But he regards this as "a municipality-specific decision. It doesn't sound like there is a rule of thumb or any trend."
Some cases Skinner sees going before the Normal Farm Practices Protection Board involve Minimum Distance Separation and odour. "It seems to me that we invite some of these situations," Skinner says. "Maybe we need to fine-tune some of that formula."
Residential lots on farm properties are a particular concern. "In many cases there probably is not sufficient distance separation," says Skinner. He thinks these farm lots "may work for one generation, but not when the property is sold out of the family." BP
© copyright 2003 AgMedia Inc..
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