Objective—To estimate the prevalence of
Mycobacterium avium subsp paratuberculosis infection
among cows on beef operations in the United
Design—Cross-sectional seroprevalence study.
Sample Population—A convenience sample of 380
herds in 21 states.
Procedure—Serum samples were obtained from
10,371 cows and tested for antibodies to M avium
subsp paratuberculosis with a commercial ELISA .
Producers were interviewed to collect data on herd
Results—30 (7.9%) herds had 1 or more animals for
which results of the ELISA were positive; 40 (0.4%)
of the individual cow samples yielded positive results.
None of the herd management practices studied
were found to be associated with whether any animals
in the herd would be positive for antibodies to M
avium subsp paratuberculosis.
Conclusions and Clinical Relevance—Results suggest
that the prevalence of antibodies to M avium
subsp paratuberculosis among beef cows in the
United States is low. Herds with seropositive animals
were widely distributed geographically. (J Am Vet
Med Assoc 2001;219:497–501)
Case Description—A 7-year-old Quarter Horse gelding used for unsanctioned racing was examined because of fever and anorexia.
Clinical Findings—Physical examination revealed fever, tachycardia, and tachypnea. Results of a CBC indicated anemia and mild thrombocytopenia. Results of microscopic examination of a blood smear indicated piroplasms in erythrocytes, consistent with Babesia spp. Regulatory authorities were contacted, and results of serologic testing at the National Veterinary Services Laboratories confirmed acute Babesia equi infection.
Treatment and Outcome—Equids on the home premises of the index horse were placed under quarantine. Those equids were tested for piroplasmosis, and 6 of 63 horses had positive results for B equi. Another horse that had previously been housed on the index premises also had positive results for B equi. Competent tick vectors for piroplasmosis organisms were not identified. All 8 horses with piroplasmosis were Quarter Horses that participated in unsanctioned racing and were trained by the same person. Two of the horses were illegally removed from the index premises; these 2 horses and the other horse with piroplasmosis that was previously housed on the index premises could not be found. The other 5 horses with piroplasmosis were euthanized. Investigators concluded that transmission of B equi among horses was most likely iatrogenic.
Clinical Relevance—The United States has been considered piroplasmosis free. However, veterinarians should consider piroplasmosis in horses with signalments and clinical signs similar to those of the index horse of this report. Regulatory authorities should be contacted regarding horses in which piroplasmosis is suspected.
Case Description—A 7-year-old Quarter Horse gelding was hospitalized in Ocala, Fla, because of lethargy, fever, anorexia, and swelling of distal aspects of the limbs. A tentative diagnosis of equine piroplasmosis (EP) was made on the basis of examination of a blood smear. The case was reported to the Florida State Veterinarian, and infection with Babesia equi was confirmed. The subsequent investigation included quarantine and testing of potentially exposed horses for B equi and Babesia caballi infections, tick surveillance, and owner-agent interviews.
Clinical Findings—210 horses on 25 premises were tested for infection with EP pathogens. Twenty B equi–infected horses on 7 premises were identified; no horses tested positive for B caballi. Seven horses, including the index case, had clinical findings consistent with EP Dermacentor variabilis was considered the only potential tick vector for B equi collected, and all D variabilis specimens tested negative for Babesia organisms via PCR assay. Results of the epidemiological investigation suggested that B equi was spread by use of shared needles and possibly blood transfusions. All horses that tested positive were involved in nonsanctioned Quarter Horse racing, and management practices were thought to pose substantial risk of transmission of blood-borne pathogens.
Treatment and Outcome—Final outcome of B equi–infected horses was euthanasia, death from undetermined causes, or shipment to a US federal research facility.
Clinical Relevance—This investigation highlights the importance of collaboration between private veterinary practitioners, state veterinary diagnostic laboratories, and regulatory officials in the recognition, containment, and eradication of foreign animal disease.