Roundworms

Nodular worm attached to intestinal mucosa

Of the helminths which parasitise in man and animal, the nematodes are those which are of the greatest economic importance worldwide. This is due to the tremendous variety of species and also to the special ontogenetic position occupied by this class of animals.

The damage which the nematodes inflict on the infested hosts ranges from organic lesions via anaemias, disturbances of the ion balance, gastric and enteric dysfunctions to major interferences with the hormonal processes and the immune mechanisms. Even neoplastic dysfunctions have been known to occur. However, the main features of the clinical processes in our domestic animals are usually diarrheas, pulmonary complaints (lung-worms, migrating larvae: cough, pneumonias, deaths), and reduced weight gains, which suggests that the chronic insidious forms are often of greater economic and epidemiological importance than the acute helminthoses (which are predominantly encountered in young animals). Phenomena such as colics and aneurysms (horses), developmental disorders, reduced milk production, poor wool quality, inferior carcass grades as well as metabolic diseases and sterility are frequent consequences of worm infestation. The resulting losses in profitability are substantial and highly relevant for the individual farm and the economy of the country as a whole.

Clinical Signs in Pigs:

Pig threadworm (Strongyloides ransomi)

Piglets become infected via the milk. Infected sows can thus infect several litters without requiring a new infestation. Infested piglets pass eggs which develop very rapidly (4-5 days) into infective third stage larvae. These penetrate percutaneously and migrate through the body. ^® Migrating larvae cause damage to the lungs (pulmonary hemorrhages, pneumonias). Parasitic female worms migrate in the intestinal mucosa: substantial losses of blood protein, debility and anemia are the result. Deaths are common in piglets. Diseased animals are already conspicuous at 2 weeks after birth: maldevelopment, lassitude, diarrheas, livid, fuliginous skin and petechiae are the principal clinical symptoms.

Lungworms (Metastrongylus spp.)

Infection only by ingestion of infested earth worms. The Metastrongylus larvae migrate through the body and settle in the lungs. Younger animals (< 1 year old) are mainly affected: bronchitis, emaciation and stunted growth are the most conspicuous symptoms. Secondary infections (bacterial or viral pneumonias) are not uncommon. - Lungworm larvae can harbor swine influenza viruses and swine fever viruses.

Red stomach worm (Hyostrongylus rubidus)

In certain regions more than 80% of all sows are infested. Larvae develop in the fundus glands of the gastric mucosa and cause nodule formation. Adult worms suck blood. The results are severe forms of gastritis, gastric ulcers and anaemias. The principal clinical symptoms are severe emaciation, agalactia in lactating sows, diarrhea and fertility disorders.

Nodular worm (Oesophagostomum spp.)

Spreading and severity of infestation increase with age. Only the colon and caecum are invaded. In reinfestations increasing tissue reactions: larvae penetrating into the intestinal wall cause nodule formation: Secondary bacterial diseases are common (paratyphoid). Clinical symptoms vary considerably: weight loss, inappetence, blood-stained slimy feces, fertility disorders.

Large Roundworm (Ascaris suum)

Migrating larvae cause lung and liver affections which in the event of reinfections can become complicated due to an increased resistance (immunity) of the body; parasitic hepatitis ("milk spots"), severe dyspnoea, cough, fever and pneumonia (enzootic pneumonia) are the result. The adult worms cause enteritis. Anemia, developmental disorders and reduced weight gains; moreover, icterus due to obstruction of the bile ducts, cyanotic manifestations and intestinal occlusion can be observed.

Whipworm (Trichuris suis)

The histotropic phase in the small intestine is followed by infestation of caecum and colon, ulcerating colitis with considerable mucus production and major changes in the blood protein picture follow. Principal clinical symptoms are evil-smelling, slimy, blood-stained diarrhea, fuliginous skin, anemia, emaciation. Deaths can occur.