Calf pneumonia: diagnostics and vaccination protocols

Transcription

1 Vet Times The website for the veterinary profession Calf pneumonia: diagnostics and vaccination protocols Author : Oliver Tilling Categories : Farm animal, Vets Date : September 28, 2015 ABSTRACT Calf pneumonia is a lifelong disease. Outwardly, calves may recover, but the internal damage to the lungs is irreversible (Figure 1) and will affect lifelong health and productivity. When the call comes in from farm clients they have calves suffering with pneumonia, a practitioner may be tempted to prescribe whatever antibiotic and NSAID are on the shelf and forget about the issue. However, a more detailed conversation and a farm visit are required (Figure 2). As with any disease, the causes of calf pneumonia are multifactorial; this article will focus on diagnosis of infectious organisms and the role of vaccination. A total of 21% of all disease in pre-weaned calves is due to pneumonia, with 22.5% of all preweaning calf deaths attributed to it (Figure 3). It is responsible for 46.5% of all post-weaning deaths 1. Calf pneumonia has a major impact on the economic performance of cattle operations. This is due to the direct costs of morbidity, mortality and treatment, as well as the long-term effects on performance. 1 / 8

2 Figure 1. Postmortem lungs of a calf that died from pneumonia. A single case of pneumonia carries a mean cost of per sick dairy calf, and a mean cost of per calf for the rest of the group 2. Add the cost of a two-week delay to first service 3, at 1.65/day 4, plus a 2.2% reduction in first lactation milk yield 3 of 165 litres (first lactation of 7,503 litres 5 ) and, once you also take into account the current average UK milk price of pence per litre (DairyCo, April 2015 price), the cost of a single case of pneumonia rises to The costs in suckler calves are per sick calf and per calf for the rest of the group 2. Calves treated for pneumonia before they reach three months are 2.5 times more likely to die after three months 6. They are 2.4 times more likely to die between three months and two-and-a-half years than heifers that have not been treated 3. They are also 2.4 times more likely to experience dystocia and will calve three months later 7. These estimates do not include a value for the welfare costs endured by the calves, nor the emotional cost to the stockman or others within the sector 8. 2 / 8

3 Figure 2. Aspects to investigating calf pneumonia. Being aware of incidence and costs, and being able to explain them to clients, is extremely useful when proposing further diagnostic testing and the potential vaccination of calves (both of which represent time and money). Readers have to decide the statement more satisfying to hear from a client: The calves are better now we treated them with that jab you gave us. We don t suffer with calf pneumonia anywhere near as much since you tested the calves, and worked out what we were dealing with. The answer of course is you want to hear both. Diagnostics The information gained from diagnostic investigations may have a limited impact on the management of a calf pneumonia outbreak as it happens, because a time delay will frequently mean the required information is not available at the time a therapeutic decision is made. However, providing a specific diagnosis of the aetiology of calf pneumonia outbreaks helps with future health planning, disease prevention and promoting animal health and welfare. It is also useful to provide evidence to support current treatment strategies, help reduce antibiotic use and maintain consumer confidence 9. 3 / 8

4 Table 1. Differential diagnoses for calf pneumonia Before taking diagnostic samples, vets should consider: Is there a requirement to take samples? What are the chances of getting meaningful results? How will the results influence what is happening on farm? Discuss animal and sample selection with the farmer to ensure testing is likely to be representative. Discuss with the laboratory where testing will take place and any doubts about submission, processing or test selection. Differential diagnoses for calf pneumonia (Table 1). Costs involved. Mixed infections are frequently present in diseased calves, and causative agents can be isolated from apparently healthy animals. Therefore, diagnostic test selection needs to be appropriate to both the disease being looked for and the animal being examined 10. Selection should: Sample calves representative of the group affected. Sample calves in the early stages of disease. Not sample chronically affected calves that have received multiple treatments it is a waste of time. 4 / 8

5 Figure 3. These calves died as a result of a Mycoplasma outbreak. Table 2 outlines preferred sampling protocols for respiratory disease outbreaks. This is a complete list, so is useful to refer to. In practice, the author does the following: Samples all calves, aged one to seven days on the day of the investigation, for their colostrum status (Figure 4). Samples six calves aged four months or older to assess historical exposure to viruses and mycoplasma on farm. Nasopharyngeal swabs on any suspected cases (up to six) of infectious bovine rhinotracheitis (IBR) and for bacteriology. Six faecal samples in cases of suspected lungworm. If a dead, untreated calf is available, conducts a postmortem at a suitable laboratory, or sends the pluck or carries out histopathology on three to four fixed samples of lung tissue, which will include border regions of healthy and unhealthy tissue. Bronchoalveolar lavage (BAL) often considered a gold-standard approach is possible, but difficulties exist. Nowhere in the UK offers the equipment, so homemade kits are required. It is also recommended samples are received by the laboratory within two hours, which represents a logistical challenge. Vaccination 5 / 8

6 Table 2. Preferred sampling protocols for calf pneumonia outbreaks The most expensive drug in the world is one that doesn t work. So while vaccination has an important role to play in the prevention of calf pneumonia, good diagnostics are required in the first place to know the causative agents. Otherwise, incorrect treatment and/or vaccines may be used with poor outcomes. Vaccines are now available that will provide effective control of the most common bacterial, viral and parasitic causes of calf pneumonia. Programmes should be designed to take into account the circumstances on individual farms and should be based around knowledge of the risk factors and the circulating pathogens 11. Vaccination programmes should reduce mortality and morbidity, improve performance, facilitate management and use of resources, have a positive effect on welfare and improve profits 12. Basic management issues must be addressed first to ensure specific pneumonia control strategies have the best possible chance of success. Fundamentally, colostrum, nutrition, environment and buildings need to be assessed. A farm visit involving everyone who has a role in caring for calves is essential for this. It could be argued all these other changes should be made first before vaccination is employed. In practice, however, making changes to existing buildings, reducing stocking rates and/or changing 6 / 8

7 feeding patterns is not always possible immediately. As much as possible should be done here first. However, the calf sits on one end of a scale, and if vaccination combined with some management changes helps to balance the scale, and stop pneumonia, it can and should be used. Vaccination is not a magic bullet, though, and can fail in the face of overwhelming pressure from pathogens. As much as possible should be done to help achieve success, namely: Ensuring vaccines are stored and handled correctly in the practice and on farm. Ensuring clients know the correct dosage and route of administration for the vaccine (clear labelling). Checking clients are aware of shelf-life and how soon a vaccine must be used once a vial is broached (usually hours). Reminding clients of the importance of using clean equipment in good working order suitable for the vaccine of choice. Vaccinating healthy calves only, and prior to stressful events such as transport, mixing or dis-budding. Vaccinating all calves in the group. Vaccinating calves at the right age (not too young). Completing vaccination courses. Disposing of unused product and containers appropriately. Being aware of adverse reactions and how to respond to them. Being aware of the advice required should a client accidentally self-inject. Reading the data sheet for the recommended calf pneumonia vaccine. Knowing how much your practice charges for a single dose and course of the vaccine. Measuring success 7 / 8

8 Powered by TCPDF ( Figure 4. Serum samples from calves aged one to seven days to assess colostrum status. A great deal of work goes into diagnosing the cause of a calf pneumonia outbreak, advising on management changes and possibly initiating a vaccination programme. This will be undermined if a follow up on progress is not made. In a perfect world, the farm client has records of morbidity and mortality for calf pneumonia, and this can be compared before and after an outbreak. If this is not the case, as a minimum, practice records of calf pneumonia drug usage can be compared and regular contact instigated with the farm client on perceptions of change. If a vet is unaware how successful advisory changes and/or vaccination programmes were, how can he or she then recommend them when confronted with a similar set of circumstances? How can he or she expect the client to purchase vaccine the following year? By taking the time to visit a farm with a calf pneumonia outbreak to offer the full package of investigatory measures, including diagnostics and possibly vaccination, the farm clinician will achieve the best chance of long-term success. This does not reduce the work received from the client quite the opposite but trust is built and the client is more likely to approach the vet for further proactive farm work. 8 / 8