Vetmargins Dr Charles Marwood talks pneumonia

With strong young stock values, pneumonia deaths are frustrating, but the longer-term costs of chronic disease and lung damage can have a huge impact on farm economics.

Poor liveweight gain has obvious impacts for pedigree and commercial animals, with lower market weights and increased time to finishing but even longer-term effects on heifer fertility and milk production end up with much higher hidden costs. Pneumonia treatments still account for most antibiotic use, but prevention is far better than cure. Management, housing, environment and vaccination status must be fully assessed if we’re looking at reducing disease.

There are many causes of pneumonia and even more risk factors and stressors which can trigger outbreaks. Having a good understanding of these is crucial to managing those risks and preventing significant losses in the short and longer term.

The incidence of pneumonia varies greatly from farm to farm, with some farms having almost negligible levels. So, what are those farms doing to manage that risk?

There are lots of different causes of pneumonia and rarely are we dealing with a single agent but several all working on top of each other. Some causes can occur so acutely they present as sudden death but usually we have a short incubation period, animals present with a fever, dull and poor appetite. Nasal or ocular discharge and a cough. At this stage prompt treatment is key to prevent the disease becoming chronic with poor long-term cures. The combination of an effective course of antibiotics and anti-inflammatories is important to improve clinical outcomes.

Classically, the Pasteurella bacteria is not difficult to treat. But even some ‘long acting’ antibiotics only cover for two-four days which may not be an effective course. Treated animal that appear to relapse often need extended treatments of antibiotics but importantly anti-inflammatories, not necessarily a different antibiotic.

Biosecurity is key to understanding risk factors – closed farms that don’t buy in any cattle have a smaller pool of virus and bacterial strains. The herd develop immunity to these strains, which is passed on to the calves via colostrum. Disease can still occur but response to treatment is often much better. Buying in animals introduces new strains of virus and bacteria, with less herd immunity this can trigger more serious outbreaks.

IBR is a herpes virus which some European countries have managed to control with vaccination and irradiation programs. In the UK, lack of legislation and vaccination, large-scale cattle movements and mixing make the IBR virus a significant risk factor.

Approximately half UK farms have evidence of IBR with infected animals becoming lifetime carriers. This means that half our farms may be naïve or free of disease but susceptible if buying cattle in. Knowing your herds IBR status is important, as biosecurity together with cheap and effective vaccination programmes allow us to control this serious disease.

Many of the other viruses that can trigger pneumonia outbreaks, like RSV, PI3 and corona virus, together with bacteria like Pasteurella, Mannheimia and Histophilus are effectively endemic on most UK farms, present in healthy adult cattle. This means these we’ll never be free of the risk, but managing the environment and maximising immunity through vaccination is key.

All year-round calving herds tend to see more respiratory disease. Mixing batches of animals with different ages and immunity is a huge risk factor for spread of disease. Many dairy herds must calve all year for level milk production but batch managing calves and not mixing is important. Automatic calve feeders and the lack of effective calf housing can make it difficult to achieve batch rearing.

There is no doubt that compact calving and managing tight age groups of animals very much reduces pneumonia risk.

Effective nutrition, optimal growth rates and trace element status, together with vaccination programmes maximises animal immunity. This won’t eliminate disease but puts the animals in a much stronger position to be able to cope with infections and fight them off.

Infected animals will shed and spread virus and bacteria into the immediate airspace. Poorly ventilated, warm, humid environments will increase the risk of outbreaks spreading. So, keeping housing clean, dry and well-ventilated at low stocking densities.

Reducing stress, handling and management procedures like castrating, de-horning and weaning should also be managed at high-risk times of the year. Also, maximising immunity before risk periods is fundamental to effective control.

We are very lucky to have lots of different vaccines available, all licenced and proven efficacy. However, some vaccines are single doses with rapid onset of immunity, but some longer lasting vaccines require a two-dose primary course. Immunity will not peak until two weeks after the second dose, so this must be considered when planning which vaccines to use and when.

Disease investigation and diagnostic testing has improved greatly in the past ten years. PCR testing from swabs and post-mortem material, and blood samples taken from recovered animals give us accurate information on the most significant pathogens on your farm. This can then be very valuable when implementing the best vaccination strategy going forward.

Pneumonia in sheep can also be a common cause of sudden death and chronic ill-thrift. Sheep vaccines against Mannheimia and Pasteurella spp are available, requiring a two-dose primary course, given to pregnant ewes and lambs.

Following data sheet dosing is important as single dosing will not provide effective immunity. These common bacteria aren’t difficult to treat with penicillins and tetracyclines, but the acute nature of these infections and serious damage caused to the lung can make treatment frustrating. Discuss the best treatment and prevention strategies with your vet during flock and herd health plans.