The lethal effects of the cibarial and pharyngeal armatures of mosquitoes on microfilariae

Abstract

Microfilariae of Wuchereria bancrofti and Brugia pahangi were killed by the chewing action of the cibarial and pharyngeal armatures and other papillae and spines in the fore-gut of mosquitoes. The proportion of ingested microfilariae that were killed was largely dependent on the presence and shape of the cibarial armature. Anopheles farauti No. 1 and Anopheles gambiae species A and B have well developed cibarial armatures and killed 36 to 96% of the ingested microfilariae. Culex pipiens fatigans has a poorly developed cibarial armature and killed only 6% of the microfilariae. Aedes aegypti and Aedes togoi lack cibarial armatures but have the remaining fore-gut structures. They killed only 2 to 22% of the microfilariae. The significance of these observations in relation to the control of filariasis with diethylcarbamazine is discussed.

The filariaLitomosoides galizaiin mites; microfilarial distribution in the host and regulation of the transmission

“…Gorirossi (1950) described epipharyngeal and hypostomal teeth in B. bacoti; their presence explains this early destruction of microfilariae. Similar events are also described in some other filaria-vector pairs (Coluzzi and Trabucchi, 1968;Bain et al, 1974;Omar and Garms, 1975;McGreevy et al, 1978;Buse and Kulhow, 1979).…”

Vectorial competence of Aedes aegypti (Linnaeus 1762) Rio de Janeiro Strain, to Dirofilaria immitis (Leidy 1856)

“…Mosquitoes are able to control the infection by D. immitis through mechanisms that reduce parasite burden by destroying or preventing the development of the nematode, i.e., well developed cibarial armature that inflict larval damage (Bryan et al 1974, McGreevy et al 1978, trapping of larvae in the coagulated bloodmeal in the mosquito's midgut (Kartman 1953), oxyhaemoglobin crystals formed by bloodmeal coagulation in the midgut that hinder the movement of mf and kill them (Nayar & Sauerman 1975, Lowrie 1991, lysis of larval cuticle by host cells (Talluri & Cancrini 1994), and encapsulation and/or melanization of the parasite in the Malpighian tubules. This last defense reaction is an important mechanism of refractoriness to D. immitis developed by mosquitoes in the genus Aedes (Lindemann 1977, Christensen 1981, Christensen et al 1989.…”

Vector competence of Culex quinquefasciatus say from different regions of Brazil to Dirofilaria immitis

“…Thus, melanization can act as an important mechanism for vector survival by limiting the number of larvae that complete development and thereby guaranteeing its own survival (Christensen 1981, Christensen & Forton 1986, Christensen & Tracy 1989. In addition, some mosquito species have well developed cibarial armature, the teeth of which, when numerous and/or developed, injuring ingested microfilariae and reducing their survival potential (McGreevy et al 1978, Coluzzi et al 1982.…”