Microfilaria

The success of filariasis eradication programs is typically gauged by the reduction in numbers of circulating microfilariae in infested individuals within a geographic area.

For members of the family Onchocercidae whose adults live in the "closed" vertebrate circulatory system, transmission to a new host is achieved by the microfilaria stage, with the help of blood-feeding arthropod vectors.

[4] The adults of E. schneideri typically reside in the carotid artery of its parasitic life cycle's definitive host, the mule deer.

Because of their size, the microfilariae pass easily through successively smaller vessels, becoming physically lodged in the small capillaries near the skin surface of the face and head.

Attracted by the carbon dioxide exhaled by the mule deer,[5] the blood-feeding female horse fly often lands on the head or face to feed.

Most recent parasitology textbooks consider the microfilariae to be "pre-larvae or advanced embryos" which will develop into the first stage larvae (L1) in the arthropod vector (p. 364[6]).

Microfilaria concomitant with metastatic deposits of adenocarcinoma in lymph node fine needle aspiration cytology: A chance finding.

Microfilaria of Dirofilaria immitis (heartworms) in a lymph node impression smear from a dog with lymphoma. This baby nematode is snuggled down in a pillow of intermediate-to-large, immature lymphocytes, exhibiting multiple criteria of malignancy (1,000X magnification; courtesy Lance Wheeler)
Microfilaria found in blood slides LACEN State Laboratory of Amazonas Brazil