Parasites of poultry are economically important for several reasons. Some transmit disease, but all cause irritation and stress to some degree and can cause anaemia through blood loss, weight loss, drop in egg production and in cases can be fatal.
The most important parasites affecting poultry in Zimbabwe are described below.
Ticks – The fowl tampan (genus Argas)
The fowl tampan is a nocturnal soft-bodied tick which hides in cracks and crevices during the day and feeds on poultry mainly at night. The female feeds on blood before laying her eggs on the bird, usually several hundred in the early stage. The larvae hatch and feed on the bird for 2 – 10 days before dropping off and moulting in 4 – 16 days. The nymph seeks the host, attaches and completes feeding in 30 minutes.
The fowl tampan transmits fowl spirochaetosis and aegyptianella pullorum. If the infestation is severe, birds will suffer anaemia from blood loss. Weight loss occurs and egg production drops.
The environment should be treated with an approved acaricide, and if birds are treated this must be done at night. Care should be taken when planning poultry houses to avoid cracks and crevices where the ticks prefer to hide.
Fleas – The stickfast (or sticktight) flea – (Echinophaga gallinacean)
Fleas are a serious pest of poultry and can cause losses due to secondary infections at the site of attachment and stress related to irritation. The fertilized females attach to the bird, usually on the head and especially around the eyes and are very difficult to dislodge. The female lays her eggs into the ulcer formed by attachment. The larvae drop off into the litter and feed off debris, including the faeces of the adult fleas. Adults can emerge after days, weeks or even months depending on suitable conditions. The newly emerged adult will seek a host, mate and the female will attach to lay and continue the cycle which can take between 30 – 60 days.
The flea transmits no known disease but secondary infections at the site of attachment can occur. Also, the irritation causes stress in the affected birds.
Treatment : Malathion 5% has been shown to be effective. Litter should be burnt between flocks to destroy the immature stages. In non-commercial flocks a dust bath containing 20% Lindane is effective and also helps to control lice.
Red Mite or Chicken Mite (Dermanyssus gallinae)
These are also nocturnal, living in crevices during the day, where they mate and lay eggs and feeding on birds during
the night. They are blood feeders and therefore a heavy infestation can cause anaemia in birds, leading to weight loss and drop in egg production. The mite can be found on the birds at night; blood on the kin or feathers may be visible.
The life cycle is very rapid, 7 days in ideal conditions, so populations can build up very quickly. The mite can survive without feeding in empty houses for up to 10 months, therefore it is essential to clean empty house thoroughly and attempt to eliminate the cracks and crevices where the mite hides. Creosote can be used to treat wood and suitable acaricides used to treat the houses when birds are not present. The chemicals should be regularly rotated.
LICE – Feather lice (Mallophaga)
The feather louse spends its entire life cycle on the host bird, feeding on dead skin and feathers, causing irritation which can become severe. The female lays her eggs which stick to the feather base. Infestation may be passed from hen to chick, or in mating birds.
The lice can be seen by parting the feathers on the breast, abdomen and under the wings. Eggs can be seen on the base of a plucked feather. Although the lice do not transmit disease, they cause irritation resulting in poor growth and decreased egg production. The resultant stress imposed can also make birds more susceptible to other disease.
Treatment of birds several times at weekly intervals can control an outbreak. All birds must be treated at the same time and it is best to treat at night. In large operations it may be necessary to destroy the infected flock and introduce strict hygiene measures before the house is used again. Care must be taken not to introduce birds carrying the lice into the flock.
SCALY LEG MITE (Knemidocoptes or Cnemidocoptes)
The scaly leg mite only infests birds. It burrows into the unfeathered skin of the head, usually the eyelids, the wattles and comb; the legs and feet and the vent, forming tunnels as it burrows, and feeding on keratin.
It completes it’s life cycle, usually about 3 weeks on the bird and does not survive for long in the environment. Transmission between birds is by close contact such as in commercial houses. The mite commonly infects older birds, causing severe weight loss and drop in egg production. In extreme cases it can cause thickening of the legs and digit necrosis. Infected birds often succumb to secondary infections through the damaged skin. The irritation can cause birds to pull out their own feathers.
The exudate resulting from the irritation causes thick crusts to develop beneath which the mites hide. These must be softened using a mild detergent or oil bases dressing before treatment can be applied.
Treatment : In small flocks, regular repeated applications of benyl benzoate may be effective in mild cases. Ivermectin and moxidectin can be applied topically or by injection. In commercial flocks, it may be necessary to destroy the infected flock; treat the buildings with acaride and leave them empty for as long as possible before introducing new birds.
REF: Dr Laura Wade : Knemidocoptes in Birds