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Heat, humidity double up on livestock

The heat, humidity and frequent showers typical of summer in Louisiana provide favorable conditions for the spread of disease and parasite problems in livestock, according to LSU AgCenter veterinarian Steven S. Nicholson.

Among the problems are mosquito-borne encephalitis affecting horses, parasites attacking sheep and goats and a variety of other diseases including pneumonia, anaplasmosis and “rain scald.”

“Mosquito-borne encephalitis has affected dozens of horses in southeastern Louisiana in recent weeks,” Nicholson said. “Both West Nile virus and Eastern equine encephalitis cases have been confirmed — primarily in animals which were not protected by vaccination.”

Nicholson said in some additional cases, horse owners were not willing to pay for blood tests, so the cause of infection is not confirmed.

The veterinarian says a major blood-sucking internal parasite of sheep and goats also is a serious problem on many farms in the Gulf Coast region.

“Larvae survive for weeks in tall, wet grass and infect the animals as they graze,” Nicholson said. “Worse yet, resistance of this parasite to approved deworming drugs further complicates the management of sheep and goats.”

Moving to another disease, the LSU AgCenter veterinarian said bacterial pneumonia is a serious health problem on cattle farms in the region.

“Cattle tend to congregate under trees during the heat of the day this time of year, and this close contact may enhance spread of respiratory infections,” he explained.

Pneumonia is a common cause of multiple cow and calf deaths during the summer, according to Nicholson, who said prompt diagnosis and treatment can limit the economic impact of the disease.

Veterinarians also are reporting outbreaks of anaplasmosis — a major problem for cattle producers to deal with in the region. Referred to as “yellow jaundice” or “anaplas,” it is spread by biting flies, mosquitoes and ticks.

“These vectors transfer blood from carrier cattle or acute cases to susceptible animals,” Nicholson explained, adding, “Three to six weeks later, signs of severe anemia appear.”

The veterinarian said some cattle infected with anaplasmosis die before signs of the illness are noticed. In other cases, the sick animal tends to remain by itself, is weak, rapidly losses weight, and in some cases may act aggressively to an approaching person.

In addition, pregnant cows that survive anaplasmosis often abort calves.

Treatment of exposed cattle with a tetracycline antibiotic can stop development of the anaplasmosis and limit further losses, according to Nicholson.

“Because of their value, annual vaccination of herd bulls is recommended, and some producers elect to vaccinate cow herds for anaplasmosis,” he said.

A skin condition called “rain scald” also is a problem on some cattle and horses this summer. Nicholson said wet skin and wounds from fly bites allow a fungus called dermatophilus to cause areas of inflammation and scabs on the skin. When the scab is peeled off, the hair comes with it, leaving a bright red moist skin lesion.

In addition, calf pneumonia, blackleg and leptospirosis have accounted for losses in some herds since early summer, the veterinarian reported.

“Livestock owners should obtain veterinary medical service for diagnosis and treatment when problems arise in their herds,” Nicholson urged. “Finding a dead or sick animal may be just the beginning of a problem that can be effectively dealt with once it is identified.”

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