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WHO/v~ctor Control/125.65 page 69

THE RICKETi'SIA vIOLBACHIA 'PIPIENTIS IN C. PIPIENS AND C. FATIGANS

by

,~_ .. __ , . J . •... deZulueta

Division of Malaria Eradication,.World Health Organization

Hertig & Wolbach (1924) described for the first time a rickettsia-like organism in the ovaries and testes of C. pipiens in the United States. A more detailed account of this organism was given later by Hertig (1936) for which he proposed the name Wolbachia pipientis. It appeared to be non-~thogenic and was found associated

in the gonads with inclusion bodies readily stained with neutral red.

ZUlueta found this organism in 1945 in C. pipiens in England and in 1947 in

C. fatigans in Colombia (South America) but his observations have remained unpublished.

Both the rickettsia and the inclusion bodies were found in the strain of C. pipiens autogenous maintained at the Molteno Institute and in wild-caught specimens of C. pipiens anautogenous from the Cambridge area. They were also found in the

C. fatigans from Villaricencio, an inland station in Colombia. As Hertig (1936) had demonstrated before, the rickettsia-like organisms could be found not only in the gonads of the adult mosqUitos, but also in the immature stages, including the eggs, but in much smaller numbers.

In this connexion it may be worth mentioning that the demonstration of Wolbachia pipientis in the gonads may appear at first difficult. In Zulueta's

experience the easiest way to prepare smears (to be stained after with Giemsa) is to dissect the ovaries (which yield the greatest nmaber of rickettsiae) and testes in an isotomic flUid, but to remove them before drying to distilled water. This helps the bursting of the parasitized cells without harm to the rickettsiae. Both the organisms from England, and Colombia, did not stain with Macchiavello. This, added to the failure to cultivate them in chicken embryo (in the case of the C. fatigans organisms) points out important differences, with pathogenic rickettsiae like those of Rocky Mountain spotted fever and typhus fever.

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vmO/Vector Control/125.65 page 70

It may be mentioned that the investi3ation of rickettsia in the gonads of several mosquito species in England yielded negc:~tive results but that a few forest culicines in Colombia ,'Jere found harbouring this on,;anism. The presence of

Volbachia pipientis in other populations of C. pipiens and C. fatigans and the exact relation of this oriSanism \iith the host species, are considered to deserve further investigation.

REFERENCES

Hertig, tvJ. & illjolbach (1922~) J. [Oed. Res., 11-)+, 329 Hertig, fIl. (1936) Parasit., 28, 11-53

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