EL PASO — Heat and dryness are probably the last things drought-battered Texans want to hear about. But if those conditions are bad for a potentially deadly parasite, Texas A&M researchers will be seeking them out.
Cryptosporidium, a protozoan parasite that may reach water supplies through dairy waste, may be rendered harmless by heat and dryness. Finding whether dairies contribute to a problem and then fixing it is the focus of a Texas Agricultural Experiment Station research project in El Paso and Stephenville.
“Once we know the fate of the oocyst stage of the parasite in dairy waste, we can determine how to handle dairy waste to reduce the chances of Cryptosporidium reaching the water supply,” said Dr. Suresh Pillai, an assistant professor of environmental microbiology with the experiment station in El Paso. “There is some indication that high temperatures and drying may cause the oocyst to lose its viability.”
Cryptosporidium is a waterborne parasite that causes the disease Cryptosporidiosis. Human sewage or animal waste can contaminate water supplies with the oocysts, a stage in the life cycle where the parasites tend to be more resistant to their environment and potentially a greater problem, Pillai said.
Disease symptoms include vomiting, diarrhea, abdominal cramps, and fever; in people with immune system deficiencies, it can be fatal. It drew national attention in 1993, when a contaminated Milwaukee public water system caused an outbreak that sickened almost 400,000 people and may have been involved in the deaths of approximately 60 others.
The parasite lives in the intestines of many animals, including one-to-four-week-old dairy calves, and also is found in feces of infected calves. It also can cause disease in cattle, sometimes fatal, and is a major concern to the dairy industry for both its human and bovine health consequences.
Because dairies often concentrate groups of cattle in small areas, dairy waste could be a factor in the presence of the parasite in water supplies, Pillai said.
If the researchers identify the factors that reduce the survival and viability of the oocysts in these wastes, they will be able to recommend changes in management of dairy waste that reduce the chances of water contamination occurring through dairy waste runoff.
The team is working at two dairy farms in Stephenville, site of the highest concentration of dairies in Texas, and at a microbiological laboratory at the El Paso experiment station.
Previous research has shown that temperatures greater than 40 degrees centigrade may destroy the viability of the oocysts. Composting of dairy waste might reduce the chances of contaminating water supplies, because organic materials generate heat as they decompose.
Allowing the waste to dry may also reduce the parasite s viability, so spreading the manure on dry pastures during dry periods may fight the spread of Cryptosporidium while serving as a good fertilizer.
The two-phase research includes testing at two dairies in the Stephenville area, where samples of both effluent from the dairy operations and from area surface water are being tested for Cryptosporidium oocysts.
At the same time, laboratory studies are being conducted in El Paso, where modifications of various dairy procedures will be tested. These include manure storage in pits or stacks, as well as liquid manure systems with storage tanks or holding lagoons, before waste is spread on dry pastures.
The entire project will involve repeated testing of waste under various conditions to see if viable Cryptosporidium oocysts are present and if they are capable of becoming infectious. Pillai and graduate student Scot Dowd have developed a way to combine detection of the oocysts and determination of their viability into a single step. That will help them save effort while examining animal wastes at different times and under different conditions to see whether potentially infectious oocysts can reach water supplies.
Dr. Forrest L. Mitchell, assistant professor at the experiment station in Stephenville, and Dr. Buddy Faries, an associate professor with the Texas Agricultural Extension Service and the Texas A&M College of Veterinary Medicine, have been working closely with Pillai and the dairies on the project. Mitchell said dairy farmers are very supportive of the research.
“We encountered no resistance in finding cooperative dairies. They consider Cryptosporidium a scourge and are ready for any sort of research solutions,” Mitchell said.
“Dairies have been getting a lot of heat for possibly contaminating water sources, but I haven’t heard of any of them who wouldn’t do what they could to stop the problems.”
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