Bovine respiratory parainfluenza-3 is a highly contagious disease and can be found all over the world. The disease is rarely fatal and usually only results mild adverse effects to the animal’s health. It is only when there are secondary bacterial infections that the disease poses any real risk. This includes a dual-infection with pneumonia.   

Bovine Respiratory Myxovirus Parainfluenza-3

This disease is caused by a virus from the paramyxovirus family and is known as the bovine parainfluenza virus type 3 (PI3). The disease is observed mostly in cattle. The pathogen adversely affects the upper respiratory tract of the cow. In most circles, bovine parainfluenza-3 is not considered to be as important a respiratory viral disease as others such as infectious bovine rhinotracheitis (IBR) and the bovine respiratory syncytial virus (BRSV).

In the majority of cases, calves are said to be more susceptible to contracting the disease. This is because their immune systems are relatively weaker than those belonging to older cows. Concerning the transmission of the disease, the virus has the ability to enter an unaffected cow via inhalation of infected aerosol droplets.

The signs and symptoms following infection include coughing, ocular, and nasal discharge, and a high temperature. Blood tests may show a small decrease in the amount of white blood cells present. Generally the signs and symptoms are relatively mild and are said to be subclinical. Vaccinations are available and to be used as preventative precautions. These vaccines can even be given safely to pregnant cows.

Transmission of Bovine Respiratory Parainfluenza-3

As with many viral infections affecting the respiratory tract in cows, the parainfluenza virus type 3 is transmitted from an infected animal to an unaffected animal. This occurs via aerosol droplets expelled by an infected cow via exhaling, coughing or sneezing, and then being inhaled by another cow. The PI3 virus has also been found to be in nasal secretions when attempts have been made in laboratories in order to isolate the virus.    

Transmission is more likely to occur if the unaffected animal is stressed due to changes in environmental temperature, surgery, an injury, dehydration, or malnutrition. Previous infection from other virus can also increase the risk of transmission.

Signs and Symptoms of Bovine Respiratory Parainfluenza-3

The mildest, and most common, form of the disease presents symptoms such as coughing, and nasal and ocular discharge. A raised rectal temperature is also often observed. The discharge in these cases begins as serous in appearance and texture. The respiration rate of the cow will also significantly increase. As the disease progresses, the discharge can become more yellow in colour. 

In its more severe form the animal becomes more susceptible to, and contracts, secondary infections. These can include infectious bovine rhinotracheitis (BVR) and, albeit mostly in calves, pneumonia. If pneumonia does occur then fatalities can generally result.

Treatment of Bovine Respiratory Parainfluenza-3

There is no medical cure against Bovine Respiratory Parainfluenza-3. Antibiotics cannot be used to destroy the virus although if a secondary bacterial infection is present or a possibility then this form of therapy may become an addition to any treatment plan. Once diagnosed, a treatment programme may begin to be put into practice. Stress is reduced and the animal is isolated in a warm and dry environment.

Prevention of Bovine Respiratory Parainfluenza-3

Vaccinations are available and can be either given intramuscularly or given via the intranasal route. They are often administered with other vaccines (combination vaccines) such as the infectious bovine rhinotracheitis vaccine. Boosters are then administered to provide the cattle with long term protection against the disease. When travelling, calves should be vaccinated.

Infected animals should be isolated to prevent further spread of the virus. Stress can weaken an animal’s immune system and make them more susceptible and prone to infection. As a result it is vital for stress to be minimised in all situations. Brought in animals should be isolated for a period of time in case they harbour a harmful pathogen prior to an introduction into the herd.

Diagnosis of Bovine Respiratory Parainfluenza-3

Diagnoses can be made following the taking of nasal swabs while the animal is still infected with the pathogen. The virus is then isolated and identified which is made easier if the animal is acutely infected with the disease. The lung tissue may also be sampled in order to achieve a diagnosis.

Prognosis of Bovine Respiratory Parainfluenza-3

The disease is rarely fatal. Only when there are secondary infections does the prognosis become poor.

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