Observations onLitomosoides Carinii(Travassos, 1919) Chandler, 1931

The host-parasite relationships in pyridoxine (vitamin B6) deficient cotton rats infected with Litomosoides carinii (Nematoda: Filaroidea)

This paper demonstrates that the establishment and growth of the filarial nematode parasite, Litomosoides carinii, is reduced in pyridoxine-deficient cotton rats. Young cotton rats were assigned to one of three dietary: vitamin B6-deficient cotton rats (B6-AL) were fed a pyridoxine-free diet ad libitum; pair-fed controls (B6 + PF) were fed the same amount of pyridoxine-free diet as animals in the deficient group and given daily oral supplements of 100 micrograms pyridoxine; and pyridoxine-sufficient controls (B6 + AL) were fed the pyridoxine-free diet ad libitum and supplemented daily with 100 micrograms pyridoxine. Half of each group was infected with 50 L3 of L. carinii by subcutaneous injection 8 weeks after the start of the experimental feeding period. B6-deficient cotton rats ate less (P < 0.001) and gained less weight (P < 0.001) than B6-supplemented controls. The levels of microfilaraemia in deficient animals, measured weekly throughout the experiment by taking blood smears, was significantly lower than in supplemented animals (P < 0.001). The deficient rats became latent for L. carinii at 20 weeks post-infection, whereas there was patent microfilaraemia in rats in the other dietary groups until the end of the experiment. Smaller (P < 0.001) and fewer (P < 0.05) adult worms were recovered from the pleural and abdominal cavities of deficient animals than from either pair-fed or sufficient controls at autopsy 28 week post-infection.

Observations on third-stage larvae and adults of Litomosoides carinii (Nematoda: Filarioidea) by scanning and transmission electron microscopy

The morphology of the body wall of the infective third-stage larvae and adults of Litomosoides carinii was studied by scanning and transmission electron microscopy. The mouth of both stages is surrounded by four inner papillae and two outer papillae; a pair of amphidial glands open laterally between the inner papillae. Female larvae and adults have two lateral caudal papillae; male larvae have a single ventral one, and adult males have two ventro-lateral lines of caudal papillae. The larval cuticle is two-layered, with fibres in the inner layer, whereas the adult cuticle has four layers apparently traversed by channels. Except for the chordal regions, larvae and adults both have an exceptionally thin hypodermis which is separated from both the cuticle and the underlying muscle cells by highly-convoluted membranes. The dorsal and ventral hypodermal chords contain nervous tissue, whereas the lateral hypodermis contains mainly mitochondria, golgi and micro-organisms. The muscle cells of larvae and adults contain thick and thin myofilaments arranged parallel to the long axis of the worms. In larvae each section has nine to 12 muscle cells, each of which has an inner non-sarcoplasmic zone containing the nucleus. The muscle cells of adult worms, although fewer in number, are more complex, and those of male worms in particular have lamellae which are deeply invaginated to form dense rectangular bands. Glycogen and lipid droplets are absent from larval muscle cells, whereas they are present in those of adult worms.

The host-parasite relationships in normal and protein-malnourished cotton rats infected with Litomosoides carinii (Nematoda: Filarioidea)

A total of 120 young cotton rats were fed ad libitum for 10 weeks on either synthetic diets containing 2.5, 5, 10 or 15% casein or on a stock breeding diet containing 20% crude protein. Half of the animals in each group were infected with the filarial nematode Litomosoides carinii and the food intake and body weight of each animal was measured. There was a trend towards increased food consumption in protein-deficient cotton rats and this was increased further in infected animals; however, differences between groups were not significant. Low protein diets reduced the rate of growth of uninfected and infected cotton rats; filarial infection intensified these adverse effects of under-nutrition and increased the number of rats which died in the lowest protein group. Protein deficiency had little effect on the number of L. carinii which developed, although fewer parasites became established in cotton rats fed on a 2.5% diet than in those fed on a 10% diet. Parasites developing in protein-deficient animals were shorter than those developing in well-fed ones and embryogenesis was retarded in female worms from protein-deficient animals. The onset of patency was retarded in protein-deficient animals and the microfilaraemia which developed subsequently was lower up to 120 days post-infection.

Vitamin A deficiency and the development of Litomosoides carinii (Nematoda, Filarioidea) in cotton rats

This paper demonstrates that vitamin A deficient (A-) cotton rats are more susceptible to infection with Litomosoides carinii than normal (A+) cotton rats. However, embryogenesis is frequently retarded in female worms from A- hosts. Groups of young cotton rats were depleted of their liver stores of vitamin A by feeding them a vitamin A free diet from weaning. From 6 weeks of age this diet was supplemented with either 2, 5, 10, 25 or 100 IU vitamin A per 100 g body weight per day and half the animals in each group were infected with L. carinii. At autopsy, 51 days post-infection, serum vitamin A levels were proportional to vitamin A intake but were unaffected by infection (P less than 0.05). A+ cotton rats grew more rapidly and gained more weight than A- ones; infected animals gained less weight than their uninfected controls. More parasites developed in rats fed either 2 or 5 IU vitamin A than those fed either 10, 25 or 100 IU (P less than 0.02) and parasites from the 5 IU group were significantly longer than those from all other groups (P less than 0.02). However, microfilarial development was retarded in female worms from A- animals as compared with A+ ones.

Suppression of microfilaraemia in Litomosoides carinii infections in cotton rats by vaccination with adult worm homogenate

Twenty cotton rats were injected with a homogentae of adult male and female Litomosoides carinii prepared by freeze-thawing the worms in phosphate-buffered-saline followed by mechanical treatment in a Potter-Elvejhma homogenizer. Intramuscular injections including Freund's complete adjuvant were made into rats which were subsequently quantitatively exposed to infection with L carinii in Liponyssus bacoti. There was no development of a microfilaraemia between 50 and 100 days post-infection in any of the 'vaccinated' cotton rats despite the presence of living adult male and female worms and microfilariae in the pleural cavity. In all the control animals and microfilaraemia developed which persisted for up to 100 days after infection.

Studies on the Malayan forest rat filaria, Breinlia booliati: periodicity and microfilaraemic patterns during the course of infection

Breinlia booliati exhibited nocturnal subperiodicity in its natural host, Rattus sabanus in contrast to experimentally infected laboratory-reared albine rats which showed irregular fluctuations of microfilariae throughout the 24 hour cycle. All the infected albino rats showed a prepatent period between 11-14 weeks postinoculation. Three patterns of microfilaraemia were discerned during the course of infection 38/49 rats displayed a single peak, 4/49 displayed 2 peaks about 12-15 weeks apart and 7/49 showed a sustained high plateau-like pattern of microfilaraemia. Cortisone had no effect on microfilarial levels when administered to rats near postpatency and some at postpatency.