Volume 12, Issue 6
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



Encapsulation of microfilariform and older larval stages of was observed among seven species of mosquitoes in British Guiana over a 2-year period. In and most of the microfilariform 1st-stage larvae were completely enclosed in a hard, thick, dark-brown capsule 12 to 24 hours after the infective blood-meal. In encapsulation often occurred within the inflated sheath. In , and , progressive stages were found 12 hours after the blood-meal, from unencapsulated to fully encapsulated microfilariform larvae and, in the latter species, also two slightly encapsulated, dead 2nd-stage larvae. In all mosquitoes encapsulation was associated with the presence of varying amounts of tiny granules, globules, plaques and flake-like debris. These were especially evident in and .

Some encapsulated 1st-stage larvae were found, along with normal ones, in 2 (0.01%) of 14,405 of the British Guiana strain and in 10 (9.8%) of 102 of the Barbados (Island) strain. This species is the major host of in both localities. No encapsulation was ever seen in , a secondary vector in British Guiana.

Most of the encapsulated microfilariform larvae were found in the hemocele, and fewer in the stomach. Rarely, encapsulated forms were found in the thorax, only in and in the British Guiana and Barbados strains of . Various stages of encapsulation are illustrated by photomicrographs.


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