Identifying, preventing neosporosis in cow herd

Identifying, preventing neosporosis in cow herd

AN often-overlooked reason for late-term abortions in gestating beef cows and heifers is neosporosis, which is difficult to prevent.

Gregg Hanzlicek, director of production animal field investigations for the Kansas State University Veterinary Diagnostic Laboratory, said the laboratory has confirmed a handful of cases in Kansas during the spring calving season.

He said neosporosis is caused by Neospora caninum, a coccidian parasite carried by both wild and domesticated dogs. It was first discovered in the U.S. in 1988, but tests on older stored tissues have confirmed the organism's presence since at least the 1950s.

"We talk a lot about it on the dairy side, but this organism is also present in beef cow/calf operations," Hanzlicek said.

Dogs, coyotes, gray wolves and dingoes are the definitive hosts of neospora, and they become infected by eating contaminated bovine tissues such as muscle, placenta and aborted fetuses, Hanzlicek said.

He explained that neospora "goes into the intestine of these canines, undergoes some changes and then is shed in the feces. It goes through another life cycle on the ground. The cow ingests the contaminated feces or ingests water or feed that contains the contaminated feces. It then moves to multiple tissues in the bovine — for example, muscles, brain and neurologic tissues and the liver."

Hanzlicek said neospora does not transmit from bovine to bovine, just from canine to bovine and back to canine. The main effect of a neospora infection is an abortion, which typically happens after three months of gestation. The most common time for the abortion to occur is during the fifth or sixth month.

Research has shown that neospora has no effect on pregnancies lasting fewer than 90 days, Hanzlicek said, but "for a newly infected herd, a lot of times, we'll see an epidemic — an abortion storm."

He defined an "abortion storm" as when more than 10% of the animals abort within a month to five-week period. Herds that have been infected for a long time typically show no visible negative effects, other than possibly having an abortion rate slightly higher than expected but not considered an abortion storm.

"Once this organism is in a pregnant animal, it gets into the placenta and causes a disruption of the oxygen transport system," Hanzlicek said. "The fetus dies and is aborted. Sometimes, the organism enters the placenta, and the cow herself will set up an inflammatory response that will abort the fetus. The other thing that can happen is the organism can enter the fetus and cause organ shutdown. The fetus dies, and again, we have an abortion."

The calves of infected cows or heifers that are not aborted have about a 90% likelihood of being born with the disease, he said. Most of these calves appear and act normally. The only time they might show problems is if they abort after becoming pregnant.

Once a cow is infected, she is persistently infected throughout life, but the risk of abortion tends to decrease as a cow ages, Hanzlicek said.

"We think (the cows), through time, set up some type of an immunity that holds the organism in check," he explained.

Tips for prevention. Hanzlicek said to help prevent the spread of neospora, producers should keep dogs from eating aborted fetuses, placentas or deceased cows or heifers that could be infected.

"A study completed some years ago indicated that a low percentage of (domesticated) dogs in Kansas were carriers of this organism," he said. "Understandably, contamination through coyotes may be more difficult to control" than through domesticated canines.

Cow/calf producers who don't feed silage or ground hay or don't feed in bunks are at a lesser risk, Hanzlicek said, because the likelihood of widespread fecal contamination of the feed or feeding area is unlikely, but there is still a danger of feces contaminating a water source.

"This disease is difficult to prevent, and testing replacements before purchase may be warranted," Hanzlicek added. "If your herd is experiencing an abortion issue, always call your local practitioner, and let them decide if neospora fits the pattern of abortion in your herd. If there is an abortion storm going on, sample the aborted fetus and placenta, and also take a blood sample from the dam."

 

BSE screening

New research from Iowa State University shows that bovine spongiform encephalopathy (BSE), a fatal neurological disease in cows, can be detected earlier by examining the animal's retina.

BSE is an untreatable neurodegenerative disorder caused by misfolded brain proteins known as prions. Classic BSE incubates for years before producers or veterinarians notice symptoms and is usually discovered when the animal can no longer stand on its own.

Heather Greenlee, an associate professor of biomedical sciences in Iowa State's College of Veterinary Medicine, said studying the retinas of cattle can identify infected animals up to 11 months before they show signs of illness.

"The retina is part of the central nervous system," Greenlee said. "Essentially, it's the part of the brain closest to the outside world, and we know the retina is changed in animals that have prion diseases."

Greenlee began studying how the retina relates to prion diseases in 2006, and the experiments that led to her most recent publication began in 2010.

The experiments utilize electroretinography and optical coherence tomography — non-invasive technologies commonly used to assess the retina. Greenlee said cows infected with BSE show marked changes in retinal function and thickness.

The results have implications for food safety, and Greenlee said the screening methods used in her research could be adopted for animals tagged for import or export as a means of identifying BSE sooner than conventional methods.

Greenlee said she is also looking at how similar diseases in other species affect the retina. For instance, she's conducting experiments to find out if retinal tissue may be a valid means of surveillance for chronic wasting disease in deer. She said she isn't ready to publish her results, but the data gathered so far look promising.

The research also may contribute to faster diagnosis of Alzheimer's disease and Parkinson's disease in humans, both of which are caused by proteins folding incorrectly.

"Our goal is to develop our understanding of the retina to monitor disease progression and to move diagnoses up earlier," Greenlee said. "We think this research has the potential to improve diagnosis for a range of species and a range of diseases."

Greenlee, in collaboration with Justin Greenlee's group at the U.S. Department of Agriculture's National Animal Disease Center, recently published findings in the peer-reviewed academic journal PLOS ONE.

 

Texas herd rebuilding

Texas cattle producers continue to slowly rebuild their herds as parts of the state deal with ongoing drought conditions.

"I don't think anybody is wholesale going out and buying bunches of cows and restocking," Dr. Joe Paschal, Texas A&M AgriLife Extension Service beef cattle specialist in Corpus Christi, Texas, said at the 2015 Texas & Southwestern Cattle Raisers Assn. Convention.

"What we're seeing is when people normally, in the past, hold back 10-15% females as replacements, they are (now) holding back maybe 20-25%, or they are going to buy some replacement females to fit that sort of bill," Paschal said. "A guy that has 100 cows that is holding back 15 heifers, ... it doesn't take long for that steady, slow, incremental process to get us back (to larger inventory levels)."

However, Paschal said drought and high cattle prices have put a lot of producers in the dilemma of choosing whether to sell out amid high prices and buy back later when cow costs come down in price.

"We are a long ways from getting back to where we were," he said. "To be honest, I don't think some folks are going to come back. As I look across the country, the big guys will come back, and some of the smaller guys may not."

Volume:87 Issue:15

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