XVII 
FILARIASIS 
FILARIASIS is prevalent both upon the coast and in the interior of Liberia. 
All the usual forms of filarial infection were met with, although filariasis was 
nowhere found to prevail very extensively. In the interior at Gbanga, about 
the geographical center of Liberia, a series of 105 natives were examined, 92 
of the examinations being made at night. Filaria (Wuchereria) bancrofti was 
found in two instances, Acanthochetlonena perstans in one instance and Loa 
loa in one instance. 
With reference to the transmission of filariasis in Liberia, Culex fatigans 
(C. quinquefasciatus), perhaps the most usual transmitting insect of Filaria 
bancrofti, was found to be present in great abundance in many localities in Li- 
beria and, indeed, was often the most common domestic mosquito encountered. 
Edwards? has demonstrated that complete development of F. bancrofti may 
occur in Taeniorhynchus africanus, Anopheles rossi, A. costalis, and A. algeriensis, 
as well as Culex pipiens. Of these only A. costalis has been found in Liberia. 
Both species of the mangrove fly, Chrysops dimidiatus and C. silacea, which 
have been demonstrated by Leiper and by Connal and Connal ? to be the car- 
riers of Loa loa, have been previously reported as having a wide distribution 
on the West African coast. In addition, other species of Chrysops were found 
during the present Expedition by Dr. Bequaert in Liberia and the Belgian 
Congo (see page 889). 
Very recently Sharp* has given evidence of the transmission of Acan- 
thocheilonema perstans by Culicoides austeni and C. grahami. The earlier work 
was done with the second species and then continued with C. austent. Sharp, 
working in Nigeria, found that after feeding upon an infected individual the 
embryos of A. perstans were ingested by the insects and that they then under- 
went metamorphosis in the thoracic muscles in the usual manner of filarial 
embryos. It was observed that the metamorphosed larvae reached the head 
and neck of the fly by the seventh day after feeding. They then pass to the 
proboscis, from which they escape by stretching, and finally bursting the ter- 
minal membranous portion of the labrum eight to ten days after feeding. 
Transmission of the parasite from insect to man was not witnessed, owing to 
the very minute dimensions of the mature larvae, but Sharp points out that 
from his investigations there is strong presumptive evidence that C. austeni is 
an efficient vector of A. perstans from man to man and that it is probable that 
C. grahami will also prove to be a natural carrier of this parasite. He points out 
1 Edwards: Jour. Trop. Med. and Hyg. (1922), XXV, 168. 
2 Connal and Connal: Trans. Royal Soc. Trop. Med. and Hyg. (1922), XVI, 64. 
3 Sharp: Trans. Royal Soc. Trop. Med. and Hyg. (1927), X XI, 70; and (1928), X XI, 371. 
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