The Damage Done by Worms

Janssen Animal Health, the makers of the wormer Flubenvet tell us about the damage that is caused  to poultry by different kinds of worms. Whilst this article is of a technical nature and originally written with commercial farming in mind, it still makes very interesting reading.

In Young Chickens

Young chickens are very susceptible to roundworm infections. Ascaridia and especially Capillaria infections will cause depressed growth and undermine the general health status of the flock. This in turn can jeopardise the applied vaccination schemes. The massive impact of ascarids was shown in a study with broiler chickens artificially infected with 500 ascarid eggs. This single infection caused serious clinical signs 6 weeks later. The chickens showed emaciation, loss of colour of combs and legs and of brightness of plumage, diarrhoea, drooping wings, ruffled feathers and a gradual loss of strength manifested by leg weakness. At autopsy, the small intestine showed external macroscopic lesions of haemorrhage and congestion.

In Laying Hens and Breeder Birds

Significant drops in egg production are apparent in infected breeders or layers because of ascarid infections. An extra concern of ascarid infection in laying hens is that occasional ascarids may undergo an aberrant migration and become incorporated into an egg. (translation by poultrykeeper: you may find a worm inside an egg!) This will be very unappealing to the consumer.

The large roundworm damage the chicken’s intestinal mucosa. Massive ascarid infection may cause intestinal blockage and possible rupture, loss of blood and nutrients.

Tapeworms do not commonly cause severe pathology in poultry, but live in the intestinal tract and compete with the host for the nutrients in the feed. The small tapeworm sticks its hooks in the folds of the intestinal mucosa. The intestinal mucosa may thereby be severely damaged and body fluids are lost.

A hairworm (Capillaria) infection can produce severe clinical signs. Affected birds appear pale and depressed, they become emaciated, develop diarrhoea and may die. Hens with capillariasis may develop a secondary vitamin A deficiency which, on top of the decreased laying rates, will cause reduced hatchability in breeders and pale yolks in layers. Gapeworms (Syngamus trachea) are a serious threat to farms with a free range management system. The gapeworm life cycle may involve the earthworm. In the earthworm, infections can persist for many years and over a period of time soil can become heavily infected. Moreover, wild birds will provide reservoirs of infection for domestic birds like turkeys, pheasants and ducks.

Left: The large roundworm damages the chicken's intestinal mucosa. Massive ascarid infection may cause intestinal blockage and possible rupture, loss of blood and nutrients.

Turkeys

Recent studies confirm that worm infections in turkeys are very common and cause considerable losses. The turkey roundworm - Ascaridia dissimilis - is a serious threat. Primarily, the larval stages give cause for concern. The intestines of turkeys often contain only few adult worms, whereas larval population is significant. These larvae cause 2 phenomena not known to most turkey breeders.

First they cause a necrotic-like enteritis, most severe in the jejunum, often with additional E. coli and/or C. perfringens infections, resulting in low weights or even mortality.
Secondly the migrating ascarid larvae may cause ‘white spots' on the liver. In young turkeys heavy infections with the ceacal worm, Heterakis gallinarum, may cause serious damage such as thickening of the cecal mucosa and petechial haemorrhages. This worm is also the transmitter of the flagellate Histomonas meleagridis. In the liver and the caecum it causes infections and diarrhoea resulting in many rejections ("blackhead"). In breeder turkeys, the tiny hairworms in the stomach (Capillaria spp.) can cause severe loses. Young turkeys are also very susceptible to gapeworm infections (Syngamus trachea).

Left: Adult gapeworms frequently obstruct the trachea, so that the bird is literally choked by the worms. This picture shows a young turkey which has died from 'gapes', in a typical 'choked' pose.

Bottom Left: Opened Windpipes of Pheasants with Gapeworms.

Pheasants and Partridges

Young pheasants are also very susceptible to gapeworm infections (Syngamus trachea). Adult gapeworms frequently obstruct the trachea, so that the bird is literally choked by the worms. The picture shows a young turkey which has died from syngamosis, in a typical ‘choked' pose. Wild animals are naturally fairly resistant to parasitic infections, but when confined in small areas, they  may become severely infected. In particular younger animals are susceptible to a vast number of parasitic infections which cause serious disease and high mortality. Syngamus trachea infection  needs to be tightly controlled, but Capillaria Ascaridia and infections are also quite common and can cause significant direct and indirect losses.