Bridging Veterinary Services Chasm to Improve Per Animal Productivity (Section 2)

Section 2:

Animal Disease Prevention: General Guidelines

 

The adage ‘Prevention is Better than Cure’, holds true even in animals since controlling a disease is more economical to farmers than treating sickness and bearing production losses. Although disease prevention programmes are easy to implement, it requires understanding of pathogenesis, the associated causal factors and long-term indulgence of the farmers in programme implementation. In general, the veterinarians tend to give more attention to microbes as the sole cause for infectious diseases. However, without the associated predisposing factors pathogens alone cannot cause a disease and precipitate it. It is easy to control a disease by manipulating predisposing factors rather than eliminating the microbes which is difficult and expensive to achieve. While attempt is made to eliminate pathogens with antibiotics, these drugs do not discriminate between ‘helpful microbes’ and pathogens. Recurrent administration of antibiotics harm ‘helpful microbes’ and hence should be used sparingly. Farm environment, especially mixture of dung, urine and water is a perfect medium for pathogen multiplication. Although microbes are ubiquitous ultimate disease causation also depends on the host response to pathogen invasion, which in turn is dictated by animal’s immune status, nutrition and general health status. Currently there is lot of interest in veterinary and medical science to understand interplay between pathogens and predisposing factors with a hope to come up with novel manipulating strategies. There is overwhelming evidence that by following important rules, animals can be reared free of many diseases. Following are some strategies to prevent infections in a dairy farm (big or small).

1. Biosecurity

For a disease to establish in farm environment, introduction of the pathogen and its spread from one animal to other is crucial. Microbes use animate and inanimate carriers to travel long distances and find new hosts. It is seen that whenever newly-purchased (disease carrier) animals are introduced in the farm, new diseases and infections also develop. The farm personnel and also visitors unknowingly carrying pathogens on their clothes and body parts are also the source of infection. Recently it has been shown that FMD virus can be carried in sufficient concentration on human clothes and body parts. Another potential source is unvaccinated stray animals that roam around the farm.

Biosecurity Golden Rules

• Restrict unwanted visitors in the farm. If that is unavoidable, restrict their entry to the outer precinct of the farm (at least 50-100 meters) so that there is no direct exposure.
• A vigilant farm management will always insist that all labour sanitise their hands, feet and face before entering the farm, preferably change to farm uniform.
• There should be barricade around the farm to avoid entry of stray animals into premises.
• Any sick animal should be separated from the herd to an isolated shed within the farm for treatment. The farm should have facilities for disposing off the dead animals.
• In multi-species farms it is better to develop independent housing for each species and the labour should not be permitted to trespass into other species area.
• Bio-medical waste from the farm should be disposed properly, preferably by hiring services of a specialised agency. The waste, if left in the farm, could become source of infection to other animals.
• While treating sick animals always use sterilised needle for each animal. It also makes economic sense to use disposable needle.
• While doing routine vaccination it may be difficult to change needle for every animal, in such situation healthy animals should be vaccinated first.
• Mosquito and other insects are potential source of infection hence the farm should have policy of controlling this menace.
• Never mix young animals with adult animals even during for a transitory period since many respiratory viruses and bacteria that are carried by immune adults can be transmitted to young ones.

 

2. Policy of ‘Closed Farm’

The strategy of getting rid of dry animals and purchasing fresh calves is a bad policy since new animals also bring new infections. For a start up farm the general policy should be to cull around 15-30 per cent animals every year for up to three years and introduce purchased animals after following quarantine measures (see box for details). As soon as farm-bred heifers are available, the policy of introducing purchased animals should be discontinued. Such farms are called as ‘closed-farm’.

Maintaining dry barn environment: Housing is a major disease determinant in cows and buffaloes. In walled barns that have improper ventilation prevalence of diseases is higher than in well ventilated barns. In tropical climate it is advisable to keep the animals in open farm with barricades around rather than wall. Floor is an important predisposing factor for foot problems, mastitis, fractures and hoof lesions. The key factor is to keep the farm premises dry all the time. Well laid and drained earth floor is the best option in areas that have low to medium rainfall. Many small farmers do not pay attention to build proper housing facilities whereas big farmers tend to over-spend and build faulty animal house. A good animal house does not mean expensive as even with modest budget it is possible to provide comfortable animal house that will ensure animal comfort and disease-free environment.

3. Maintaining proper stocking density

This factor is very crucial since increased density of animals at the farm would also enhance chances of contact. Many respiratory disease outbreaks, especially in young calves, have been reported in farms where stocking density becomes high. Usually calf housing is not paid much attention and during calving season suddenly numbers increase leading to outbreak of respiratory diseases. In controlling outbreaks there is a simple intervention called ‘dilution effect’ wherein the stocking density is reduced to at least half by relocating animals to nearby open area. It is important that farmers realise their farm stocking threshold and follow this strictly.

4. Manure management

This aspect of farm management is largely neglected by small and large farmers. Manure should be collected and stored at a distance from the main farm and the farmers’ house else it may lead to propagation of insects endangering the health of family and the farm animals. In case animals are kept on open earth floor, the manure gets sun-dried and its handling is easier. If the manure is to be used in agriculture, it is better to transport and store it near the cultivation area. If the impact on family’s and animals’ health and the resultant costs is considered, it is always economical to invest in manure management options, like converting it to organic fertiliser, methane gas and electricity. 

5. Proper and complete treatment of sick animals

Any sick animal at the farm should be treated as potential threat to other animals hence due care should be taken to ensure that diseases do not spread. Antibiotics administration should be in the right dose and for right duration, even if the animal has shown improvement in first few injections. Half-way left treatment results in emergence of resistant bacteria becoming harmful to humans and animals. Biomedical waste such as placenta, swabs, wound dressing material; surgically removed tissues should be disposed off after sanitising in formalin solution or by employing certified biomedical waste disposal agency. In India it is a criminal offence to dispose biomedical waste in an open field. 

6. Balanced nutrition

Good nutrition means feed that is natural to animal species and balanced nutrition is that which would satisfy the energy requirements for physiological maintenance as well as for production. In case of dairy animals, the correct strategy is to supply maximum energy through good quality green and dry fodder and the concentrate (grain-based ration) should only be a source to supplement the deficiency. In case of ruminants since digestion is by anaerobic fermentation with the help of rumen microbes, giving uniform feed throughout the year keeps the animals free from many digestive and metabolic disorders. Any change in feed must be done gradually over a week. Stored fodder and feed such as silage, dry grass could also be source of infection, hence quality assurance is necessary.

7. Regular Vaccination

Animals should be vaccinated against common endemic diseases regularly. In order to prevent disease outbreaks at least 90 per cent animals in the herd should be vaccinated at the same time and if this is not followed vaccinated animals may remain protected but disease would continue to recur in the farm. In case the disease still persists after vaccination of the entire herd, expert veterinarians should be consulted to undertake antibodies titer studies to understand vaccination failures. While vaccinating, the instruction on storage, reconstitution and disposal should be followed as faulty storage destroys potency of vaccine leading to vaccination failures. Table 4 describes the general vaccination schedule but the farmers are advised to consult their veterinarian to add or delete vaccinations depending upon the local endemic diseases and the outbreak pattern.

Table 4: Vaccination schedule in cows/buffaloes/calves.

Vaccine	Dose/Route	Immunity	Time of vaccination
Foot and Mouth Disease Polyvalent vaccine	3 ml or as per manufacturer’s recommendation, subcutaneous	Six months to one year	February or December, or in the event of an outbreak, or when large scale cattle movement is expected
Hemorrhagic Septicemia	5 ml, subcutaneous	One year	May-June, or just before onset of monsoon
Black Quarter	5 ml, subcutaneous	One year	May-June
Anthrax-spore vaccine	1 ml, subcutaneous	One year	Done only when an outbreak has been reported or May-June when the area is known to be endemic
Brucellosis–Cotton Strain-19	2 ml or as per manufacturer’s recommendation, subcutaneous	Life-long	Usually undertaken in young calves aged 4-8 months. Adult cows/buffaloes can also be vaccinated if the farm is highly endemic. RB-51 vaccine should be used
Theilariosis: Cattle and calves above 2 months of age	3 ml, subcutaneous	One year	No specific time but preferably prior to summer onset.

Note: Farmers are advised to consult their veterinarian to add or delete vaccinations depending upon the local endemic diseases and the outbreak pattern.