Disease in cattle is characterized by fever, anorexia, and difficulty swallowing. The swallowing disorders are caused by damage to the striated muscles of the pharynx, larynx, esophagus and tongue, and may lead to dehydration, emaciation, and aspiration pneumonia. Edema, hemorrhages, erosions, and ulcerations may be seen in the mouth, on the lips, and around the coronets. The animals may be stiff and lame, and the skin may be thickened and edematous. Abortions and stillbirths have also been reported in some epidemics.

Most EHDV infections in cattle appear to be subclinical. Typical symptoms include fever, oral ulcers, salivation, lameness associated with coronitis, and weight loss. In pregnant cows, the fetus may be resorbed or develop hydranencephaly if it is infected between 70 and 120 days of gestation. Deaths are uncommon with the North American strains of EHDV; however, some animals may be lame and unthrifty for a prolonged period.

Most outbreaks of EHD occur in late summer or early autumn. The onset of freezing weather usually stops the appearance of new cases, but hoof sloughing can be seen throughout the year.

Among the Cervidae, EHD is most severe in white-tailed deer. In this species, the morbidity and mortality rates may be as high as 90 percent. Severity of the disease varies from year to year. It also varies with the geographic location. In the U.S. Southeast, most cases are mild and mortality rates are low. In the Midwest and Northeast, EHD typically recurs each year, but can vary from a few scattered cases to severe epizootics with high mortality rates. This variability is thought to be caused by many factors including the abundance and distribution of the insect vectors, the EHDV serotype, existing herd immunity, and genetic variations in the susceptibility of the host. Surviving deer develop long-lived neutralizing antibodies. Nearly 100 percent of the deer population can be seropositive in some regions.

New Mexico biologists say tissue samples are currently being processed by the state veterinary lab.

Officials advise hunters to be vigilant for deer, elk or antelope that have unusual behavior or appear sick. Animals that demonstrate the symptoms of EHD should not be harvested and hunters should report anything unusual to the Department of Fish & Game. The toll free number to call is (888)-248-6866.


Also of interest on Southwest Farm Press:

NRCS in Texas announces incentive payments to improve wildlife habitat

TAHC seeks comments on rule changes for disease rulings

Fox rabies may be back in Central Texas after cow tested positive