| Adult
Parascaris
equorum
are stout, whitish worms, up to 30 cm long, with 3 prominent lips. The life cycle is similar to that of
Ascaris
suum
(the roundworm of pigs,
Ascaris
sp
), with a prepatent period of 10-12 wk. Large numbers of infective eggs can remain viable for years in contaminated soil. Adult animals usually harbor very few worms. The principal sources of infection for young foals are pastures, paddocks, or stalls contaminated with eggs from foals of the previous year.
|
| In heavy infections, the migrating larvae may produce respiratory signs (“summer colds”). In heavy intestinal infections, foals show unthriftiness, loss of energy, and occasionally colic. Intestinal obstruction and perforation have been reported. Intestinal stages compete for absorption of essential amino acids. Diagnosis is based on demonstration of eggs in the feces. If disease due to prepatent infection is
suspected, diagnosis may be confirmed by administration of an anthelmintic, after which large numbers of immature worms may be seen in the feces. |
| On farms where the infection is common, most foals become infected soon after birth. As a result, most of the worms are maturing when the foals are ~4-5 mo old. Treatment should be started when foals are ~8 wk old and repeated at 6- to 8-wk intervals until they are yearlings. All broad-spectrum equine anthelmintics are effective against the adult and immature worms in the small intestine and, therefore, ascarids are readily controlled by routine anthelmintic administration. In
cases in which verminous pneumonia due to
Parascaris
migration has developed, therapeutic benefit may be achieved by treatment with ivermectin or fenbendazole (the latter at 10 mg/kg/day for 5 consecutive days) concurrent with appropriate antimicrobial therapy.
Parascaris
infection can be effectively prevented by daily administration of pyrantel tartrate once foals are eating grain regularly. |
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