Acanthocheilonema sabanicolae n. sp. (Filarioidea: Onchocercidae) from the savanna armadillo (Dasypus sabanicola) in Venezuela, with comments on the genus Acanthocheilonema.

A new species of Acanthocheilonema, Acanthocheilonema sabanicolae n. sp., is described from the subcutaneous tissues of the savanna armadillo (Dasypus sabanicola) in Venezuela. The adults (females 25-30.6 mm long by 61-78 micron wide; males 10.9-15.3 mm long by 42-44 micron wide) and the microfilariae (112-131 micron long by 3-5 micron wide) are the smallest within the genus. The microfilaria, a skin dweller, assumes a characteristic C-shaped curve, when fixed in 2% formalin, which serves to distinguish A. sabanicolae from others in the genus. Moreover, the spicules are notably smaller than any others in the Acanthocheilonema. Acanthocheilonema sabanicolae is the first species in this genus to be described from edentates, and, along with A. reconditum of dogs and A. pricei of opossums, is the third species of Acanthocheilonema to be reported from South America. Morphological features, vectors, and vertebrate hosts of the genus Acanthocheilonema are reviewed.

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.

On Dipetalonema viteae infection of Mastomys natalensis.

Experimental infections were carried out with the tissue-dwelling filaria Dipetalonema viteae using the argasid tick Ornithodorus moubata as the intermediate and the multimammate rat Mastomys natalensis (Strain GRA Giessen) as the final host. The optimum infective dose was found to be 50 third-stage larvae, which produced patent infections and the recovery rates of adult parasites were 47.6 and 26.4% of the inoculated larvae 140 and 189 days after infection, respectively. After an average prepatent period of 57 days, the microfilaraemia increased progressively and reached relatively low maximum values about 192 days after infection. These maximum values were followed by rapid decrease of microfilaraemia, but microfilariae were still detectable at 261 days post infection. Following the subcutaneous injection of infected animals with dexamethasone in single doses each of 1, 10 or 20 mg/kg body weight 30 minutes before blood puncture, a dose-dependent increase in the microfilarial counts in the circulating blood was observed, this reaching maximum values between 120 and 160 days after infection. Repeated administration of single doses of 10 mg/kg dexamethasone revealed an uniform but temporary increase in the microfilaraemia but this was not associated with any alterations in the reproductive organs of adult female parasites. No correlation could be found between the number of microfilariae in the circulating blood and the number of adult worms recovered from the subcutaneous connective tissue. At necropsy 300 days after infection living female parasites could not be found any more.

Kinetics of Dipetalonema viteae infections established by surgical implantation of adult worms into hamsters.

Native LVG strain hamsters were infected with Dipetalonema viteae by the surgical implantation of adult worms. Groups of hamsters received either 50 male, 50 female, 50 male plus 50 female or 25 male plus 25 female worms per hamster. Approximately 50% of the transferred worms became established in the recipient hosts regardless of the number or sex of the worms implanted. Microfilaremia occurred in recipient hamsters within 1 week after the transfer of female or male plus female worms. This microfilaremia became negative on week 9 post-transfer and no microfilaremia developed in these hamsters following a secondary challenge infection of male plus female worms. Hamsters whose primary infection consisted solely of male worms developed a microfilaremia when challenged with male plus female worms.