Also known as
Elaeophora is a genus of parasitic nematodes (roundworms). These internal parasites live inside and attached to the interior surfaces of major arteries, veins and/or heart chambers in various ruminant hosts including cattle, sheep, deer, elk and moose. Infestation with various Elaeophora species is referred to as elaeophorosis.
The various species of Elaeophora have been found in Africa, Asia, Europe, and North America. This particular species was first seen in Water buffalo in 1879, and named Filaria poeli.
In 1912, it was reclassified into the newly named genus Elaeophora, after one study found it to be the same worm that previous authors had referred to as Filaria blini and Filaria haemophila, both of which were isolated from Water buffalo aortas.
E. poeli has since been found in several species of cattle: African buffalo, Water buffalo, and Zebu. The geographic distribution of this species includes several Asian and African countries (Democratic Republic of Congo, India, Indonesia, Malaysia, Mozambique, the Philippines, Tanzania, Thailand, Uganda, and Vietnam).
In spite of the fact that the damage from these worms produces aneurysms (bulges and ballooning weaknesses) in the arteries and heart of their hosts—aneurysms that can measure up to 2 centimeters in diameter--clinical signs of the worm infestation are seldom noticed or reported, with the exception of E,schneideri infestation in sheep, elk, and moose.
In sheep, for instance, these worms are often found in every artery large enough to accommodate them and sometimes obstruct blood flow. In some of the smaller arteries, reduced blood flow can cause blindness, deafness and other signs, and if a blocked artery or aneurysm ruptures, the animal may bleed to death.
These worms also cause severe itching dermatitis and the affected sheep may rub so much that they injure the skin.
In cattle, however, the affects and damage caused by these worms is generally not enough for the animal to show any signs.
The percentage of animals found to be infested in large-scale slaughterhouse studies range from 1.7% in Tanzanian Zebu to over 60% in Philippine domestic water buffalo. A study of free-ranging buffalo in Queen Elizabeth National Park, Uganda, showed a 55% infestation rate.
- Clinical signs mild or unnoticed
Elaeophora poeli is a large nematode, with male worms measuring 45–70 mm long, and females 40–300 mm long, though the microfilariae (immature stages) are much smaller. Although these worms live in nodules and aneurysms in the walls of the aorta and heart, they rarely cause clinical signs.
The life cycle of E.poeli is still not known. The adults usually live attached to the inner walls of the aorta. They create aneurysms (bulging nodules) in the walls of the aorta, which can be up to 2 cm in diameter.
The male worm lives curled up and encysted inside the nodule, while the female lives with its head inside the nodule and its body free in the interior of the aorta. It is presumed that the female sheds offspring (microfilariae) directly into the bloodstream.
Adults have also been found in nodules on the epicardium (inner layer of the pericardium—the sac of fibrous tissue that surrounds the heart and the base of its major blood vessels).
The nodules and bulges in the aorta wall could conceivably rupture if they become too large. Corrugated and migratory tract lesions on the inner wall of the aorta, and fibrin strands attached to the aneurysms have also been reported. One study found narrowing of the aorta down to 1/3 of its usual diameter in some cases.
Despite the presence of nodules on aorta walls and heart tissue, and narrowing of the aorta, almost all studies of E. poeli infestation mention a lack of obvious clinical signs in infested animals, though one study found a strong correlation between infestation and visceral pleurisy (inflammation of the membrane inside the chest that surrounds the lungs). Heavy infestations may cause fibrous thickening of the blood vessel walls.
Since cattle rarely show signs of infestation, prevention is usually not a concern.
Not knowing whether a herd is infected or not makes treatment decisions difficult, though routine deworming for other internal parasites may reduce these worms as well.