HERD HEALTH
PIH-38
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Pseudorabies (Aujeszky’s Disease, Mad Itch)
Authors
C. John Mare' University of Arizona
Don P. Gustafson, Purdue University
L. W. Schnurrenberger, USDA, Washington, D. C.
Reviewers
Robert Bennett, Linden, Indiana
Robert D. Glock, Iowa State University
Willard Korsmeyer, Beardstown, Illinois
Introduction and History
Pseudorabies (Aujeszky's disease) is an acute, frequently fatal disease affecting most species of domestic and wild animals; however, man and the higher apes are resistant. 

The disease is caused by a virus of the Herpesvirus group and is characterized by a variety of clinical signs, those involving the nervous and respiratory systems being particularly prominent. Severe itching and self-mutilation are seen in most species, but rarely in swine.
The disease was first recognized as a disease of cattle and dogs in Hungary by Aujeszky in 1902. It soon became evident, however, that swine were the natural hosts of the virus and that pigs could also die of the disease. In Europe, pseudorabies has been recognized for many years as an important cause of death in swine of all ages and also as a cause of abortion. In the United States, the disease was until recently considered to be important only as a cause of death in baby pigs and occasionally in cattle, dogs and cats. It has become evident, however, that pseudorabies is not only more prevalent in this country than was formerly believed to be the case, but that the present viruses are capable of causing a wide variety of clinical manifestations, including death in newborn and adult swine and fetal death with abortion in pregnant swine. Although the disease is widespread and of considerable economic importance in several midwestern states, a slaughter serum survey conducted in 1977-78 revealed a nationwide incidence of only 3.73%.
Clinical Signs

Pigs less than three weeks old. In baby pigs, the disease may be characterized by sudden death with few if any clinical signs. More often, death is preceded by fever which may exceed 105°F, dullness, loss of appetite, vomiting, weakness, incoordination and convulsions. When vomiting and diarrhea occur, the disease in baby pigs closely resembles transmissible gastroenteritis (TGE). In pigs less than 2 weeks old, death losses frequently approach 100%. Baby pigs may have become infected before birth and die within 2 days of birth, occasionally after showing violent shaking and shivering (shaker pig syndrome). Piglets in-
fected immediately after birth may show clinical signs within the first 2 days of life and usually die before they are 5 days old.

Pigs three weeks to five months old. After 3 weeks of age, pigs usually develop a degree of resistance to the disease, and death losses may decrease from about 50% in pigs exposed when 3 weeks old to less than 5% in pigs exposed when 5 months old. Death losses do vary however with different strains of the virus, and even in grown pigs severe death losses occasionally occur.

Fever is a prominent clinical sign in these growing pigs and is usually followed by loss of appetite, listlessness, labored breathing, excessive salivation, vomiting, trembling and eventually marked incoordination, especially of the hind legs. Death is usually preceded by convulsions. Involvement of the respiratory tract with sneezing, rubbing of the nose and coughing may occur. Clearto yellowish nasal discharges may be seen. Infected pigs which recover will usually have lost condition and will be slow to reach market weight.

Mature pigs. The disease in adult pigs is usually not severe, but with some strains of pseudorabies virus deaths may occur in grown pigs. The disease in adult pigs is often characterized by fever and respiratory signs such as nasal discharges, sneezing, nose rubbing and coughing. Nervous signs such as trembling, incoordination and itching occasionally occur, and blindness may rarely follow pseudorabies infection. Vomiting and diarrhea or constipation may be seen.

Sows infected in the early stages of pregnancy may return to heat because of death and resorption of their fetuses. Sows infected in middle pregnancy may eventually abort mummified fetuses, whereas sows infected late in pregnancy often abort or give birth to weak, shaker, or stillborn pigs. Piglets infected prior to birth usually die within 2 days.

Postmortem Lesions
No gross lesions characteristic of pseudorabies are consistently found. Small greyish-white spots of focal necrosis may occur in the livers and spleens of pseudora-
Cooperative Extension Work in Agriculture and Home Economics. State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. G Diesslin, Director, West Lafayette, IN.  Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age or handicap.