Calf pneumonia

Dairy calves are likely to suffer from the disease at any age, with it manifesting itself as a chronic, coughing pneumonia, or as a more acute, enzootic calf pneumonia. Older dairy calves are also vulnerable after housing in the autumn. Suckler calves are more likely to suffer from respiratory disease between two and five months of age, following weaning or transport from one herd to another. Outdoor reared beef suckler calves can also be severely affected by pneumonia.

Causes

In older calves, mainly in weaned suckler calves aged six months to two years, respiratory disease is likely to occur after transport or other environmental stress and is often called shipping or transit fever. Similarly, a respiratory disease caused by lung parasites, husk, occurs in older calves.

However, it should be remembered that lungworm can occur in young calves, even when housed if exposed to significant challenge from carrier dams or contaminated bedding A viral respiratory disease caused by the infectious bovine rhinotracheitis virus.

Aetiological agents

Enzootic pneumonia in calves is a multifactorial disease. Infectious agents, environment, management and the immune status of the calves are all-important factors in determining the outcome of an infection.

A multitude of infectious agents, including viruses, bacteria and Mycoplasma spp (M. bovis, M. dispar and M. canis), are involved in different combinations on different farms. It is often suggested that the viral and mycoplasmal agents are the primary infections and the bacterial agents cause a secondary infection in an animal whose defences have been weakened by the first infection.

The most common viral agents isolated from enzootic pneumonia cases are respiratory syncytial virus (RSV), parainfluenza III virus (PI3) and infectious bovine rhinotracheitis virus (IBR), some of which are discussed separately as herd problems elsewhere in the compendium.

Bovine viral diarrhoea virus (BVD), has also been implicated in the bovine respiratory disease complex, not as a primary pathogen, but as a disease agent causing immunosuppresion.

Mycoplasmal agents are usually considered to be the most common agents causing the chronic form of enzootic pneumonia, even though Mycoplasma bovis has been identified as the causative agent in many acute outbreaks as well.

The most commonly isolated bacterial organisms are Pasterurella multocida, Mannhaeimia haemolytica and Hemophilus (Histophilus)subspecies (H. somnus).

Predisposing factors

The main environmental factor predisposing calves to respiratory disease is poor ventilation in calf housing. Cold, humid conditions, sudden changes in air temperature, stress due to different causes and change in the environment have also been associated with outbreaks of pneumonia in young calves.

Inadequate intake of colostrum or poor quality colostrum will affect the calves' defence against respiratory agents and make them more susceptible to infection. Weaning of calves before five weeks of age has been associated with increased respiratory disease.

Rearing systems where calves of different origin are mixed together at a young age suffer from high levels of respiratory diseases. Large, shared air spaces, calves from different age groups and poor sanitation between calf batches often make these systems even more vulnerable. Calves that have suffered from diarrhoea are also more likely to suffer from respiratory disease. The stress associated with management procedures such as disbudding and castration may also be associated with a high respiratory disease incidence.

Effects

Calf pneumonia can potentially be a significant economic burden to a farm, due to the costs of treatment, mortalities, reduced growth rates, additional labour and housing requirements.

Diagnosis

Enzootic pneumonia in young calves may be a chronic disease with very few clinical signs apart from a dry cough and slightly increased respiratory rate. The acute form of the disease usually manifests itself in an outbreak involving several calves going down with the disease within a 48-hour period. Fever, dullness, inappetance and coughing, often combined with nasal discharge, are the most common symptoms.

Respiratory diseases are considered the second most important cause of death and ill drift in calves. The condition is farm related, with some farms suffering serious losses due to calf pneumonia, while on others the disease is either very mild or non-existent. Sporadic outbreaks can, however, be experienced by farms that normally see very little respiratory disease in calves.

Treatment & Control

Whilst it is important to identify the infectious agents in outbreaks of enzootic pneumonia on an individual farm basis in order to target prevention and control of this disease complex, there are some common approaches to husbandry and management that are likely to reduce the incidence of enzootic pneumonia, independent of the causative factors. These approaches can be divided into three areas:

1. Maintenance of disease resistance;
2. Reduction of stress; and
3. Reduction of exposure.

Maintenance of immune status:

• Do not separate the dam until 24 hours after calving
• Provide adequate bedding to allow the calf to stand without difficulty
• Ensure early colostrum feeding; assist if needed, and monitor the intake as closely as possible and record it ("maximum supervision, minimum interference"). Calves should consume approximately 10% bodyweight in colostrums in the first 6 hours of life (i.e. approximately 4-5 litres for an average calf, or, a minimum of “6 pints in 6 hours”)
• Keep a supply of frozen colostrum in case the dam leaks colostrum before calving
• Avoid stress and exposure to new disease agents during "poor immune capacity" at 2-4 months of age
• If immunosuppressive respiratory pathogens are a known herd problem (i.e. BVDV), consider eradication or vaccination
• Vaccinate strategically as a part of a comprehensive disease control plan

Minimisation of exposure:

•  Provide adequate numbers of calving pens and clean and disinfect them between batches
• House calves of different ages in different rooms or with adequate separation
• Quarantine bought-in animals for 2-3 weeks before introduction to the rest of the herd
• Provide good ventilation in the calf housing - a minimum of 6m³ airspace for calves up to 6 weeks old; 10m³  for calves up to 2 weeks and 15m³ for calves up to 16 weeks old. There should not be excessive humidity in the calf house
• Consider calf hutches.  

Reduction of stress:

• Avoid overcrowding in calf pens
• Provide good ventilation (There should be 6 air changes per hour)
• Make sure that calves are well bedded during cold weather and do not suffer from draught (the minimum critical temperature for newborn calves in a straw bedded pen is 6ºC)
• Provide shelter during prolonged cold and wet conditions on pasture
• Avoid transport and introduction to new environment between 2 and 4 weeks of age
• Time castration and disbudding away from weaning
• Time autumn housing away from castration and disbudding
• Introduce diet changes gradually, particularly when housing calves

Medication/Vaccination

In the face of an outbreak of enzootic pneumonia in a closed herd or when a chronic problem is recognised, it is important to attempt to identify the causative agents and management and environmental factors in order to target preventive measuresin the future.

There are a number of investigative techniques that can be used in the face of a pneumonia out break. These include taking nasal swabs and / or bronchioalveolar lavage (BAL) samples for bacterial culture and virus isolation. Additionally, paired blood samples can be taken to assess serological immune response to respiratory pathogens. However, reliance on paired serological testing must be done with caution as false negatives (failure to seroconvert) can occur in young calves less than 3 months old.

For the acute form of enzootic pneumonia,nursing and isolationof affected calves is important in all treatment regimes. Vitamins can be administered as a supportive therapy, and a multitude of treatments from antihistamines to expectorants have been found effective in alleviating the condition. Antimicrobials and both steroid and non-steroid anti-inflammatory drugs are usually the main line of treatment. Antibiotics can be used in in-contact animals (metaphylaxis) as well as in the affected ones. Vaccines can occasionally be used for the in-contact animals, and have been shown to provide protection when the causative agent is identified fast enough.

Many of the antibiotics used in the treatment of enzootic pneumonia, particularly to give protection to in-contact animals, are long acting formulations with very long statutory withdrawal periods of up to 60 days. Whilst withdrawal periods are seldom a major consideration for drug choice in young animals, the veterinary surgeon is responsible for advising the farmer with respect to the withdrawal period for any product used, so that particularly in calves which may be sold or enter the food chain out of the current farm’s control.

The chronic form of enzootic pneumonia is normally not treated unless the calf has a severe cough. Antibiotics, when chosen carefully, may be effective, although severe lung damage may not resolve. It should, however, be noted that chronic enzootic pneumonia in calves is a herd problem.When the condition becomes severe enough to require treatment, it is necessary to attempt to identify the causes of the condition. Improvement of the management and environment or eradication of the causative agent/agents with the help of a comprehensive disease control plan is required.

This information was taken from: 

http://www.vetsweb.com/diseases/calf-pneumonia-d223.html

See more information:

http://www.thecattlesite.com/diseaseinfo/176/calf-pneumonia

http://homepage.eircom.net/~progers/0calfimm.htm