zoonoses and communicable diseases common to ... - PAHO/WHO

PASTEURELLOSIS 201Bovine hemorrhagic septicemia is caused by P. multocida serotype 6:B in Asia,and by 6:E and 6:B in Africa. In fibrinous pneumonia (“shipping fever”) in cattle,serotype 1 of P. haemolytica, and serotype 2:A of P. multocida predominate.CATTLE: Shipping fever, also called bovine respiratory disease complex, is a syndromethat causes large economic losses in the cattle industry of the WesternHemisphere. In the US, it causes annual losses estimated at more than US$ 25 million.Shipping fever is an acute respiratory disease that particularly affects beefcalves and heifers as well as adult cows when they are subjected to the stress of prolongedtransport. The symptomatology varies from a mild respiratory illness to arapidly fatal pneumonia. Symptoms generally appear from 5 to 14 days after the cattlereach their destination, but some may be sick on arrival. The principal symptomsare fever, dyspnea, cough, nasal discharge, depression, and appreciable weight loss.The fatality rate is low.The etiology of the disease has not been completely clarified, and it is noteworthythat the disease does not occur in Australia, even when animals are transportedover long distances (Irwin et al., 1979). Several concurrent factors are believed tocause the syndrome. Most prominent among these are such stress factors as fatigue,irregular feeding, exposure to cold or heat, and weaning. Viral infections, whichoccur constantly throughout a herd and are often inapparent, are exacerbated by factorssuch as overcrowding during transport. Moreover, susceptible animals suddenlyadded to a herd lead to increased virulence. The virus most often identified as theprimary etiologic agent is parainfluenza virus 3 (PI3) of the genus Paramyxovirus.Infection by this virus alone usually causes a mild respiratory disease. However, thedamage it causes to the respiratory tract mucosa aids such secondary invaders as P.multocida and P. haemolytica, which aggravate the clinical picture. On the otherhand, virulent strains of Pasteurella can cause the disease by themselves.Pasteurellae frequently isolated in cases of shipping fever include P. haemolyticabiotype A, serotype 1, and various serotypes of group A of P. multocida. The factthat treatment with sulfonamides and antibiotics gives good results also indicatesthat a large part of the symptomatology is due to pasteurellae. Another importantviral agent that acts synergistically with pasteurellae is the herpesvirus of infectiousbovine rhinotracheitis. Similarly, viral bovine diarrhea, chlamydiae, and mycoplasmascan play a part in the etiology of this respiratory disease.An important disease among cattle and water buffalo in southern and southeasternAsia is hemorrhagic septicemia. In many countries, it is the disease responsiblefor the most losses once rinderpest has been eradicated. Hemorrhagic septicemiaalso occurs in several African countries, including Egypt and South Africa, and, lessfrequently, in southern Europe. The disease seems to be enzootic in American bison,and several outbreaks have occurred (the last one in 1967), without the diseasespreading to domestic cattle (Carter, 1982). In tropical countries, hemorrhagic septicemiaoccurs during the rainy season. The main symptoms are fever, edema, sialorrhea,copious nasal secretion, and difficulty in breathing. Mortality is high.Surviving animals become carriers and perpetuate the disease. Cases of hemorrhagicsepticemia have also been recorded in horses, camels, swine, yaks, and otherspecies. It must be borne in mind that hemorrhagic septicemia is due to the specificP. multocida serotypes 6:B and 6:E. There is no evidence that the disease occurs indomestic cattle in the Americas.