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Published Date: 2013-05-21 11:07:21
Subject: PRO/AH/EDR> Equine piroplasmosis - USA: (TX)
Archive Number: 20130521.1727066

EQUINE PIROPLASMOSIS - USA: (TEXAS)
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Date: Mon 20 May 2013
Source: Texas Animal Health Commission (TAHC) news release [edited]
http://www.tahc.texas.gov/news/2013-05-20-KlebergCountyPiroTestingUpdate.pdf

Texas Animal Health Commission continues testing equines in Kleberg County for piroplasmosis
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The Texas Animal Health Commission (TAHC) designated Kleberg County (South Texas) equines (horses, donkeys, ponies, mules, and zebras) as high risk for exposure to equine piroplasmosis (piro) in March 2013. As a result, the TAHC began mandatory testing of all equines in Kleberg County on [8 Apr 2013]. The initial Kleberg County test zones extended south from Escondido Creek to the Kleberg-Kenedy county line.

Equine piroplasmosis (piro) is a blood-borne protozoal disease that affects all equines, but is not transmissible to humans. Through research, a treatment protocol has been developed that can often clear the infection and lead to the release of horses that tested positive. Piro is currently not considered endemic in Texas or the US; however, isolated outbreaks of the disease such as in Kleberg County have occurred.

Piro can be transmitted from a positive horse to a negative horse by blood transfer from dirty instruments or by tick vectors. South Texas has a large and diverse population of ticks. Horses visiting pastures with infected tick populations can become infected as a result. Once positive horses are treated or removed, the tick populations within those pastures free themselves of the disease in approximately one year, and it will be safe to put negative horses back in the pasture.

"Because piro is considered a foreign animal disease to the US, it is important we make every effort to find undetected cases in the area," said Dr Dee Ellis, Texas' State Veterinarian. "We believe the piro situation related to tick transmission in Texas is limited to just a few south Texas counties. The TAHC is asking for the support of local horse owners to ensure this testing effort is a success." Horse owners are also encouraged to discuss the situation with their local veterinarian.

To date, 283 premises and a total of 747 equine animals have been tested in Kleberg County as part of the county wide testing effort. Of the premises and animals tested, 6 premises have tested positive with a total of 19 total horses involved.

The TAHC is hoping to wrap up testing in the southern part of the county by the end of May [2013], where approximately 30 premises remain to be tested. The next efforts will involve testing the northern part of Kleberg County. All equine owners in the county who have not had their equines tested are strongly encouraged to contact the TAHC as soon as possible to schedule an appointment. Equine owners can call (361) 676-0979 to set up an appointment. The test is free of charge.

"We greatly appreciate the cooperation of the equine owners and veterinary practitioners of Kleberg County, and the high level of voluntary compliance with the mandatory testing requirement," said Dr TR Lansford, Region 5 Director. "We look forward to working with the remaining owners of untested equines and the local veterinarians as we strive to complete the area test in Kleberg County. It is important that all equines are tested as soon as possible."

Kleberg County equine owners and/or veterinary practitioners who have questions should contact the TAHC Region 5 Office in Beeville at (361) 676-0979. For more information on piroplasmosis they can also visit http://www.tahc.state.tx.us/animal_health/equine/piro.html.

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Communicated by:
Bonnie Ramirez
TAHC
<bonnie.ramirez@tahc.state.tx.us>

[Equine piroplasmosis results from infection by the protozoa _Babesia caballi_ or _B. equi_ (phylum Apicomplexa). The 2 organisms may infect an animal concurrently.

Equine piroplasmosis is a tickborne protozoal infection of horses. Piroplasmosis may be difficult to diagnose, as it can cause variable and nonspecific clinical signs. The symptoms of this disease range from acute fever, inappetence [lack of appetite], and malaise, to anemia and jaundice, sudden death, or chronic weight loss and poor exercise tolerance. The disease may be fatal in up to 20 percent of previously unexposed animals. The tick vectors exist in the United States, and epidemics of piroplasmosis were seen in Florida in the 1960s.

The incubation period for _B. equi_ infections is 12 to 19 days, and infections are more severe. For _B. caballi_ infections, it is 10 to 30 days.

The clinical signs of piroplasmosis are variable and often nonspecific.
In acute cases, the animal is usually emaciated, jaundiced, and anemic. The liver is typically enlarged and dark orange-brown. The spleen is enlarged, and the kidneys are pale and flabby. Petechial hemorrhages may be seen in the kidneys, and subepicardial and subendocardial hemorrhages in the heart. There may also be edema in the lungs and signs of pneumonia. In chronic cases, common symptoms include mild inappetence, poor exercise tolerance, weight loss, transient fevers, and an enlarged spleen (palpable on rectal examination). Foals infected in utero are usually weak at birth, and rapidly develop anemia and severe jaundice.

The differential diagnosis for piroplasmosis includes surra, equine infectious anemia, dourine, African horse sickness, purpura hemorrhagica, and various plant and chemical toxicities.

Equine piroplasmosis can be diagnosed by identification of the organisms in Giemsa stained blood or organ smears. _B. caballi_ merozoites are joined at their posterior ends, while _B. equi_ merozoites are often connected in a tetrad or "Maltese cross." Organisms can often be found in acute infections, but may be very difficult to find in carrier animals. In carriers, thick blood films can sometimes be helpful.

Because _Babesia_ organisms can be difficult to detect in carriers, serology is often the diagnostic method of choice. Serologic tests include complement fixation, indirect fluorescent antibody (IFA), and enzyme-linked immunosorbent assays (ELISA). The IFA test can distinguish between _B. equi_ and _B. caballi_.

Other methods of diagnosis include DNA probes, in vitro culture, and the inoculation of a susceptible (preferably splenectomized) animal with blood from a suspected carrier. In addition, pathogen-free vector ticks can be fed on a suspect animal, and _Babesia_ identified either in the tick or after the tick has transmitted the infection to a susceptible animal.

Disinfectants and sanitation are not generally effective against the spread of tick-borne infections. However, preventing the transfer of blood from one animal to another is vital.

Portions of this commentary have been extracted from http://www.cfsph.iastate.edu/Factsheets/pdfs/equine_piroplasmosis.pdf.

Kleberg and Kenedy counties in south Texas can be located on the map at http://www.digital-topo-maps.com/county-map/texas.shtml. - Mod.TG]

[_B. caballi_ in blood smear:
http://www.daff.gov.au/__data/assets/image/0010/1596574/fig2.gif
- Mod.JW

A HealthMap/ProMED-mail map can be accessed at: http://healthmap.org/r/6Z7G.]

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