Parasite-induced suppression of the immune response in Aedes aegypti by Brugia pahangi.

The melanization response against intrathoracically inoculated Brugia pahangi and Dirofilaria immitis microfilariae (mff) isolated from vertebrate host blood was evaluated in both uninfected Aedes aegypti black-eyed Liverpool strain and in mosquitoes harboring a developing B. pahangi infection. The immune response against inoculated mff of either species was significantly reduced by 28-47% in infected as compared with uninfected mosquitoes. Attempts to passively transfer this suppression factor(s) by inoculating naive mosquitoes with 0.1-0.2 microliter of hemolymph from B. pahangi-infected mosquitoes produced equivocal results. The role this parasite-induced immune suppression might play in aiding parasite survival in compatible vectors is discussed.

Increased activity of macrophages from mice infected with Brugia pahangi: in vitro adherence to microfilariae.

After the inoculation of infective larvae of Brugia pahangi into the peritoneal cavities of CBA/Ca mice adult worms developed, but by 12 weeks post-infection the parasites were usually dead and surrounded by granulomatous tissue. Macrophages were the most common cell type in these granulomas and were also found in increasing numbers free in the peritoneal cavity. We have investigated the ability of macrophages to damage microfilariae in vitro, in a system where microfilariae were cultured together with cells and serum taken from either uninfected female CBA/Ca mice or at various intervals after infection. Macrophages adhered to and killed microfilariae in this system and there was an increase in vitro adherence of these cells during the course of infection. The peak level of in vitro activity of these cells coincided with the phase of parasite killing in vivo. The presence of serum also affected the degree of macrophage adherence and subsequent death of the parasite. Analysis of serum components using EGTA, zymosan or heat inactivation suggested that complement and possibly heat labile antibody were involved. Immunoglobulins were shown by immunofluorescence to be present on the surface of microfilariae cultured in serum from infected mice. It is concluded from this study that macrophages are actively involved in the termination of murine filarisis.

Cryopreservation of third-stage larvae of Brugia malayi and Dipetalonema viteae.

Methods are described for the cryopreservation of third-stage larvae of Brugia malayi. Optimum conditions utilized larvae free from the mosquito host frozen at the rate of -1 degree or -0.8 degrees C per min in medium containing 9% dimethyl sulfoxide and 0.004 M polyvinylpyrrolidone. Nonfrozen or thawed larvae were inoculated intraperitoneally into jirds (Meriones unguiculatus), the thawed larvae after cryogenic storage for 5-378 days. In general, the percentage of adult worms recovered at necropsy was comparable between the two groups and ranged from a mean of 6-9% of the larval inoculum. In addition, three of four patas monkeys (Erythrocebus patas) inoculated with thawed B. malayi larvae developed patent infections. The cryopreservation of third-stage larvae of Dipetalonema viteae also is discussed.

[Diaplacental transmission of microfilaria of the species, Brugia pahangi, in the cat]. / Diaplacentare Ubertragung von Mikrofilarien der Art Brugia pahangi bei der Katze.

Eight kittens born of two Brugia pahangi infected cats have been studied for transplacental passed microfilariae. In the peripheral blood microfilariae could not be demonstrated at any time. However, in the lung of a young cat killed two days post partum ca. 30 microfilariae have been found (microfilaremia of the mother 90 mf/20 mm3). Histological studies suggested two possibilities of transplacental passage--by blood and by secretion of the uterus glands.

Experimental infection of Rattus sabanus and Rattus muelleri with subperiodic Brugia malayi.

R. sabanus and R. muelleri are very common in the lowland forests of Malaysia. In nature they are infected with Breinlia sp. and D. ramachandrani. In an attempt to determine whether they are also susceptible to subperiodic B. malayi and thereby being potential reservoirs of infection of the disease, 24 R. muelleri and 17 R. sabanus were experimentally infected with the parasite. Results show that although they can support the full development of the parasite, they are poor hosts. This confirms the observation that in Malaysia natural infection of Rattus spp. with the parasite has not been seen. These rats therefore are probably not important in the zoonotic transmission of subperiodic B. malayi in Malaysia.