Elaeophora poeli

Elaeophora poeli is a parasitic roundworm that infects the aorta—and occasionally the heart—of several cattle species across Asia and parts of Africa. These worms are relatively large: males range from 45 to 70 mm in length and 200 to 260 μm in width, while females measure between 40 and 300 mm long and about 350 μm wide. Their offspring, called microfilariae, are 340 to 346 μm long and 7.0 to 7.5 μm wide. Although the worms create bulging nodules (aneurysms) in the aortic and heart walls, noticeable illness in infected animals is rarely reported.

The species was first described in 1879 from water buffalo and named *Filaria poeli*. In 1912, it was moved to the newly created genus *Elaeophora*. A detailed redescription in 1938 showed that *E. poeli* was the same organism earlier authors had called *Filaria blini* and *Filaria haemophila*, both also found in water buffalo aortas.

*E. poeli* has been recorded in African buffalo (*Syncerus caffer*), water buffalo or carabao (*Bubalus bubalis*), and zebu (*Bos indicus* or *Bos taurus indicus*). Its geographic range includes the Democratic Republic of Congo, India, Indonesia, Malaysia, Mozambique, the Philippines, Tanzania, Thailand, Uganda, and Vietnam.

The worm’s full life cycle is unknown. Adults typically attach to the inner wall of the aorta, where they form aneurysmal nodules up to 2 cm in diameter. The male curls up inside the nodule, while the female keeps its head in the nodule and its body free in the aorta’s interior. It is thought that females release microfilariae directly into the host’s bloodstream. Adults have also been found in nodules on the heart’s epicardium.

Infection rates in large slaughterhouse studies vary widely: from 1.7% in Tanzanian zebu to over 60% in Philippine water buffalo. A study of free-ranging buffalo in Uganda’s Queen Elizabeth National Park found a 55% infection rate.

The nodules are aneurysms that could theoretically rupture. Other changes include corrugated lesions and migratory tracts on the inner aortic wall, as well as fibrin strands attached to the nodules. In some cases, the aorta’s diameter narrows to one-third of normal. Despite these findings—including 2-cm nodules on the aorta and heart—most studies note a lack of obvious clinical signs. One study did find a strong link between infection and visceral pleurisy (inflammation of the lung’s outer membrane).