key: cord-023711-xz5ftnat
authors: MORENO-LÓPEZ, J.
title: Acute Respiratory Disease in Cattle
date: 2013-11-17
journal: Virus Infections of Ruminants
DOI: 10.1016/b978-0-444-87312-5.50075-8
sha: 
doc_id: 23711
cord_uid: xz5ftnat

nan

Acute respiratory disease in cattle is a serious problem in countries with intensive or semi-intensive systems of feeding and management. The etiology is complex and many reviews list the microorganisms incriminated. Some of the viruses which can infect the respiratory tract of cattle are summarized in Table  34 .

Viruses and bacteria, together with physical stress, transport, overcrowding, irregular feeding and poor standard of hygiene as well as environmental factors (ventilation, temperature and humidity) play an important role in pathogenesis.

The disease has world-wide distribution. It affects cattle of all races and ages, tends to recur and responds poorly to preventive and therapeutic treatment. Even if the disease for the most part occurs during calfhood, adult cattle may also be involved. 

The symptomatology of acute respiratory disease is similar in different outbreaks and includes depression, inappétence, dullness, increased respiration and pulse rates in the early stages. The respiratory disorder may or may not be accompanied by diarrhea.

Acute respiratory disease in cattle is not attributable to a single etiological agent. In many instances, mixed infections with two or more agents occur, as shown in Table 34 . Such mixed infections can contribute to the severity of the disease. Moreover, the microorganisms involved appear to act synergetically. Examples of synergism have been demonstrated in the USA (shipping fever, caused by parainfluenza-3 (PI3) virus and Pasteurellae) and Sweden (Umeâ disease, caused by PI3 virus and BVDV).

It is difficult to estimate the economic losses, but in terms of mortality, loss of milk production and delayed weight gains, the acute respiratory disease is considered as one of the most costly and troublesome problems for the cattle industry.

It is generally accepted that viruses are the primary agents and that bacteria like Pasteurellae may, as secondary invaders, accentuate the pathology of the respiratory tract, as in "shipping fever". Some of the viruses are circulating in the cattle population, as for instance PI3 virus, which is common in the respiratory tract and is easily transmitted. High percentages of seropositive animals were found in various countries. Serological surveys have shown that, on the contrary, BVDV was much less frequent on farms separated geographically than on farms with a close contact of animals on common pastures. Collectivization of calves with a different immunological status like that occurring on breeder farms or in large feedlots, leads to accumulation of viruses introduced by animals in the incubation or convalescence stages or by latent carriers. Under these circumstances, explosive outbreaks of respiratory and enteric disease may occur. It is unknown how stress factors during massive transport and crowding promote pathogenicity of various respiratory viruses, because it is not possible to mimic a natural outbreak by experimental infection. All too frequently only a mild disease is reproduced. Some of the viruses per se have an adverse influence on defence mechanisms. It was shown that infection with PI3 virus may initially diminish the cell-mediated immune response; also, BVDV may act on lymphocytes and neutrophils, suppressing antibody production and phagocytosis, respectively. Suppression may promote invasion of other agents, particularly through close contact and crowding in stables lacking proper ventilation. As regards diagnosis, a somewhat pathetic conclusion can be drawn: if foot-and-mouth disease virus is isolated from an animal, the disease has been identified. However, if PI3 virus or BVDV has been isolated, you have diagnosed the infection but not an "acute respiratory/enteric disease", because other viruses and also bacteria might be etiologically involved.

As diagnostic techniques become more widely applied, an increasing number of viruses has been isolated from cattle with acute respiratory disease. At the end of the 1950s, "shipping fever" was described as a disease following massive transports to or from the enormous feedlots of the USA, and PI3 virus was isolated as the first virus of a condition with a multiple viral etiology.

In Sweden, at about the same time, there were outbreaks of a severe acute respiratory-enteric syndrome on farms in the Umeâ district in the northern part of the country. Local veterinarians provisionally called the syndrome "Umeâ disease". Thus BVDV became the second member of a multiple etiology.

At that time, PI3 virus was suspected to be the cause of the infection in the respiratory tract (manifested by tracheitis and pneumonia), and BVDV to be the cause of infection in the intestinal tract (manifested by erosions in the oral and intestinal mucosa). Both viruses were indeed identified. However, it has to be kept in mind that the terms "parainfluenza" and "bovine viral diarrhea" are merely taxons by which these viruses are classified.

During the following decade, the first two bovine adenoviruses (types 1 and 2) were described in the USA, and subsequently a third type was identified in the UK. These are the isolates that grow in kidney cells with a hexon antigen common to all mastadenoviruses. Then Hungarian workers reported the isolation of two new bovine adenoviruses, types 4 and 5, which preferentially grow in cultured calf testicle cells. Then additional adenoviruses, types 6 through 8 were reported as "testicle-cell types" from various countries and, finally, from Bulgaria, a type 9 being a "kidney-cell type". Regarding the "testicle-cell type" adenoviruses, the proof for the presence of antigen(s) common to mastadenoviruses is equivocal at present. The types 4, 5 and 7 have been described each as a single causative agent of acute respiratory-enteric disease in Hungary and Japan, respectively.

During the 1970s the first records appeared on bovine respiratory syncytial virus (BRSV), closely related to the human respiratory syncytial virus and causing pneumonia in cattle often less than 2 years of age. BRSV was found either as a single agent or as a member of a multiple etiology (as recently reported from UK and USA) condition.

In some countries the bovid herpesvirus-1, better known as infectious bovine rhinotracheitis (IBR) virus, is a "solo" pathogen. IBRV was the first viral agent definitely shown to cause respiratory infection in cattle. Herpesvirus type 3 (malignant catarrhal fever virus), with a low and sporadic incidence, is also incriminated in the bovine respiratory-enteric disease complex.

The role of herpesvirus type 4 (prototype strain Movar 33/63) has not been elucidated. However, a respiratory illness caused by this virus in association with Pasteurella multocida was quite severe.

It is easy to extend this listing by adding, for example, bovine enteroviruses, rhino-and parvoviruses, coronaviruses and the reoviruses. The isolation of these viruses from apparently healthy cattle as well as from those with acute respiratory-enteric disease indicates that they are widespread. However, because they appear to be infrequently implicated in disease processes, it seems that they cause infection only under certain conditions. Bacteria such as Chlamydia, Pasteurellae and mycoplasmas may influence the cycles of infection with viruses.

Young animals require more care than adult animals. Calves fare best when confined individually or in very small groups. This facilitates individual observation, control of diseased animals and maintenance of a higher standard of hygiene. A large number of animals maintained in close contact provides ideal conditions for the spread of disease agents via the respiratory tract. The immunological status, especially passive immunity of the animals, is important in connection with respiratory disease. Protective titers of serum antibodies have been calculated for some of the respiratory pathogens. PI3 virus infection seems to be prevented by a serum neutralizing antibody titer of 32 and IBRV infection by a titer of 2. The significance of local nasal antibodies and CMI against respiratory disease is of special importance.

With the complex etiology as that associated with respiratory infections it

is logical that control measures are not easy. Control of the disease may be attempted by diminishing the frequency of infections and by implementing a vaccination program against the most frequent agents. Some authors have tried to suppress infections by interferon or interferon inducers, i.e. avirulent viruses known to stimulate nonspecific defence mechanisms, including interferon production; however, no efficient control procedures have become available. The development of effective and practical vaccines for the prevention of respiratory disease is notoriously difficult, due to the multiplicity of agents which are involved. As shown in Table 34 , at least 15 distinct microorganisms have been identified. Certain viruses, however, produce more severe disease than others; vaccines against them may be expected to break the chain of events leading to respiratory disease.

The multiplicity of agents necessitates the use of polyvalent vaccines; polyvalence does not appear to affect the immunogenicity of the individual agents. Although desirable, the incorporation of all potential pathogens in a single vaccine is difficult, if not impossible. The results of some limited field trials with a tetravalent vaccine have in no way been encouraging.

Finally, it must be reemphasized that a problem of this complexity is not solved by a single measure but demands that attention is given to both the infectious and environmental causes of the disease.

A serosurvey of viruses during outbreaks of acute respiratory and/or enteric disease in Swedish cattle