By Makeli Phiri
PARASITIC helminths may be found in most internal organs, but chiefly in the alimentary tract, the liver and the lungs. Internal parasites are those larger organism that live inside and attack some part of the body of domestic animals.
Hleminths may be divided into two kinds, the flat worms and round worms. There are a number of factors that affect the worms:
• Warm moist conditions – these aid speed hatching of worm eggs, likewise such conditions help larvae to survive and increase range of movement of larvae.
• Cold conditions – these make conditions unfavourable for hatching and reduces active movements. The direct sun and dryness is lethal on the larvae and eggs.
• Long leafy grass – this protects by giving shade and retaining moisture and the rain, physically breaks dung piles, spreading larvae over a wide area.
• Number of animals – obviously the more animals there are on any given area the greater chance larvae have of finding a host.
What about pasture ecology. This is highly significant under intensive grazing systems, where maximum pasture production is aimed at using fertiliser and planted grasses.
Thus the strain of grass and the amount of fertiliser used influences growth, as does the rainfall and temperature.
While long leafy grass improves the condition of animals and so increase their resistance, it also favours the worms by giving shelter from harmful weather.
Another factor is the natural scouring effect of high protein grass, which tends to spread larvae and allow easy escape from faeces.
The stocking density obviously affects the length of the grass. If it is very high the grass will soon get short (which favours destruction of worms) but it also means that animals will easily infect each other.
They may be forced to eat grass soiled with dung or at least graze very close to piles of dung, something they avoid doing if they have plenty of space.
If the stocking density is very low, grass will not be eaten and therefore be wasted, the long grass protects larvae and keeping the animals in the paddock for a long time to try and use the grass, slowly but continuous buildup of infection may finally result in cases of gastro enteritis.
As a farmer, what husbandry method would you use, considering all the factors mentioned here, to give maximum benefit to the animal and least to the worm population?
Liver flukes as the name says, this kind of worm inhabits the bile ducts of the animals especially cattle and sheep. They can be many in this organ.
They cause loss of condition and poor growth. Furthermore, flukes cause a very wasteful loss of livers when beasts are slaughtered.
Money spent on dosing for flukes is very well spent. The gain is that the farmer is likely to many times the cost of the medicine. In fact where fluke is present, dosing will improve production more profitably than any other kind of routine dosing or injection.
However, the farmer must understand that the liver is the organ used for the de-toxification of poisons, drugs and unwanted substances. In bad fluke cases the liver may be destroyed so whatever drug is used there may be serious intoxication and even death of the animal.
It must equally be known that a large number of flukes killed by dosing may block the bile ducts, go rotten and cause complete collapse of the liver and death.
If as a farmer you are making an initial herd dosing, first get abattoir reports on liver and laboratory reports on dung samples from 10 to 20 percent of the herd.
Here assessment of the herd would be made on the level of infection. Advice on trial dosing, watch for bad reactions, then advise a dose rate and which classes of stock should be left un-dosed. Start with young stock and leave older stock.
For the control measures, control of snails may often be impractical where large areas of the farm is swampy or where dambo grazing is a vital dry season supplement. Even if a fencing scheme would work it may be too expensive to justify the expected extra profit.
Farmers have options that is if consultation has been made with veterinary or animal husbandry officers in their area of farming activities.
LIVESTOCK WORMS DURING THE RAIN SEASON
