The disease is caused by a single virus or a combination of more than one virus affecting the respiratory tract. It has been based on the isolation of virus, serological evidence, and pathological lesions of viral pneumonia. It is often complicated by secondary bacterial invasion which exacerbate the initial infection. Though the role of Chlamydia sp. in the disease is not clear, these organisms have also been associated with respiratory disease in Kids as a part of mixed infection. The possible role of rhinovirus, reovirus and enterovirus cannot be ruled out. Viruses cannot be isolated at necropsy from all the cases because virus is cleared and secondary bacterial infections (most commonly Pasteurella sp.) result in mortality. Organisms belonging to Mycoplasma capri, M. dispar, urea plasma sp. and Pasteurella hemolytic are the common secondary invaders to primary infection in Kids pneumonia.
WHY KID PNEUMONIA GETS AGGREVATED
Unhygienic environmental conditions like overcrowding, poor ventilation and stress are considered to be important factors in precipitating the disease. The morbidity and mortality rates vary considerably depending on the condition of housing, management, and the kind and number of viruses and bacteria that are involved in the infection. The morbidity rate may reach up to 100% but the case fatality rate is usually less than 5%. Morbidity rate of 80-90% with case fatality rate above 30% may be encountered in the acute respiratory syncytial viral pneumonia of Kids. The infection spreads mostly by aerosol and direct contact with the infected individuals particularly in a poorly ventilated and unhygienic environment.
HOW THIS DISEASES PROGRESS IN THE RESPIRATORY SYSTEM OF GOATS
The viral interstitial pneumonia caused by the respiratory viruses affect the cranial lobes of the lungs and result in either sub clinical, mild clinical or severe and highly fatal form of the disease. Parainfluenza-3 virus causes sub clinical pneumonia if not invaded by the secondary organisms. Such cases are not very serious whereas clinical signs like coughing and polypnoen may be seen in mild cases of the disease. In severe form like in respiratory syncytial viral infection. There is severe dyspnoea with open mouth breathing and expiratory grunt. However toxaemia is not noticed as usually recorded in bacterial pneumonia. Bacteria may sncondarily invade after the establishment of primary viral pneumonia. Such secondary bacterial pneumonia varies depending upon the species of bacteria responsible for the condition and response to specific therapy. However, bacterial infection may recur if the viral pneumonia is extensive. The virus particles produce pathogenicity by reducing the mucosal resistance thereby allowing the bacteria to invade the tissues, and also destroy the cilia of the bronchial mucous membrane, which helps to keep the lower respiratory tract pathogen free. Rhinitis, tracheitis, bronchitis, proliferative and exudative bronchiolitis with alveolar collapse and multinucleated syncytial giant cell formation in the epithelial linings are seen in bovine respiratory syncytial virus infection.
Clinical findings of goat pneumonia
The clinical signs vary in severity but they are more or less similar in pneumonia caused by viruses. Many Kids are usually affected during the acute viral pneumonia. Initially, moderate rise in body temperature (104-105°F) harsh hacking cough, which is increased on squeezing the trachea from outside, polypnoea. Rhinitis as evidenced by mucopurulent nasal discharge, and sometimes diarrhoea are noticed. The Kids often remain mentally alert. Auscultation of the thorax reveals abnormalities in the apical and cardiac lobes of lung with loud and harsh breath sounds. Generally, the affected Kids recover gradually in a few days time unless a more severe bacterial pneumonia develops. In secondary bacterial bronchopneumonia, fever, dyspnoea and toxaemia usually become more severe. Body temperature may rise organisms invade the lungs. The affected area of lung is increased, harsh breath sound becomes louder and it is followed by crackles and pleuritic friction rubs. Such cases can be managed successfully. When it is invaded by Corynebacterium phogenes, marked consolidation of lung, profound toxacmia and loud breath sound are commonly noticed. A similar clinical picture is also seen in Fusobacterium necrophorum infection but in such cases, necrotic lesions can also be recorded in mouth and/or larynx, and the animal responds well to antibacterial therapy.
Irrespective of the specific cause, common necropsy lesions include bilateral area of collapse with little bronchiolar reaction, emphysema and dark and consolidation of lungs, inflammatory changes in the nasal mucosa, and congestion of lungs. Interstitial pneumonia, emphysema, severe bronchiolitis and alveolitis with multinucleated syncytia containing intracytoplasmic inclusion bodies are important pathological lesions in respiratory syncytial viral pneumonia.
The characteristic lesions in Pasteurelle multocida invaded tissue are extensive hepatisation with mottled red and grey lobules, considerable interlobular aggregations of serofibrinous fluid and a fibrinous pleurisy. Extensive consolidation and supeuration of lung tissue occur in Corynebacterium pyogenes and Fusobacterium necrophorum infections.
Broader diagnosis of pneumonia in Kids may be easy but specific aetiological diagnoses are difficult. The Kids that are maintained indoors and reveal clinical signs like coughing, tachypnoea, nasal discharge, and fever can be diagnosed as suffering from viral pneumonia. In other cases, the disease can be diagnosed On the basis of clinical signs, necropsy lesions and isolation of the organism. For isolation swabs from naso-pharynx transtracheal aspirates or lung lavage samples may be collected In outbreaks, antimicrobial sensitivity test of the isolate becomes important. Isolation of the bovine respiratory syncytial virus is difficult because of its fragile nature. Therefore for its diagnosis, the serological tests like virus neutralization, modified indirect fluorescent antibody, complement fixation, indirect haemagglutinatio and ELISA have been recommended. Of these, EL ISA test is usually preferred because of its accuracy and less time requirement. The disease should be differentiated from verminous pneumonia, interstitial pneumonia, pneumonic pasteurellosis, and aspiration pneumonia as well as from congenital cardiac defects. Lungworm pneumonia is usually recorded in Kids, which are allowed to graze in pasture. Coughing, marked dyspnoea, fever moist loud crackles over the dorsal area, loud breathing sounds on the ventral aspect of lungs and few deaths are the usual findings. The acute interstitial pneumonia occurs in cattle of 6 to 18 months of age, and is characterized by severe dyspnoea, fever, loud breath sounds over the ventral aspects of lungs and failure to respond to antibacterial therapy. In pneumonic pasteurellosis, fever, toxaemia, depression, loud breath sounds over the ventral aspects of lungs and clinical improvement with antibacterial therapy are noticed. History of faulty feeding or drenching or oral medication in Kids followed by acute dyspnoea, anxiety and distress usually indicates aspiration pneumonia. Though some affected Kids may survive, others succumb in a short period. Acute myocardial dystrophy is characterized by tachycardia, cardiac arrhythmia, pulmonary oedema and weakness of skeletal muscles.
The rational approach to manage a case of Kids pneumonia includes removal of the environmental factors, treatment with antimicrobial drugs and other adjunct therapies. The affected Kids must be removed from the environment, which is considered to be unhealthy and harbour the pathogens. The animals should be kept in an airy, well- ventilated, clean and dry place.
Though cases suffering from viral pneumonia do not respond well to antimicrobial drugs, use of antibacterial drugs becomes necessary keeping in view the chances of secondary bacterial infection. The treatment should be initiated at the earliest. For such purpose, broad spectrum antibacterial drugs are usually preferred. Sulphonamides such as sulphadimidine @150 mg/kg b wt either parenterally or orally daily for 3 to 5 days have been proved effective. Other drugs like streptopenicillin, tetracycline, chloramphenicol or amoxycillin may also be given with a good success rate. Tetracycline can be added to feed @ 10-20 mg/kg b wt daily for 3 weeks and may be given as a follow-up therapy to improve the convalesence, performance and prevent relapses. Pneumonia complicated by bacteria can also be treated with these antibacterials.
The adjunct therapies may include use of different bronchodialators, analgesics, anti-inflammatory agents, steroids and antipyretics depending upon the clinical signs present. The choice and dose of such drugs would wholly depend on the judgment or the attending clinician.
Prevention and control of goat pneumonia
Since inadequate husbandry practices predispose the Kids to the disease, so the chances of occurrence of enzootic pneunomia in Kids can be minimised by providing a healthy environment. Avoidance of overcrowding and poor ventilation and following of quarantine procedures for new entrants can help in preventing the disease. Attempts can also be made to maintain a favourable environmental temperature and any sudden change in the climatic condition should be noticed and, if possible. Necessary measures be adopted. In the areas with a long winter, special precautions are required particularly to avoid exposure to inclement weather, to provide adequate warmth and bedding, and to provide optimum nutrition.
Another important measure is to feed sufficient quantities of colostrum during the early hours of life so that natural resistance against the diseases can develop. Attempts have also been made to use prophylactic vaccines to prevent the occurrence of Kids pneumonia in different countries. However due to lack of satisfactory results and scientific trials, it has not yet been recommended for use in the Kids at field levels in the country.