Studies on the kinetics of expulsion by guinea-pigs of primary infections with the intestinal nematode parasite Trichostrongylus colubriformis

Heston strain guinea-pigs were infected with 1000 Trichostrongylus colubriformis infective larvae and the kinetics of parasite expulsion from the host studied. Expulsion began approximately 15 days after infection, after which log worm count declined from an initial level of approximately 2·77 at a rate of approximately 0·1 per day. There was no significant difference in worm counts in each sex.     

Capillaria hepatica infection of Mastomys natalensis: on the development, egg production and host reaction (author's transl)]

Studies on the development and egg production of Capillaria hepatica and on the macroscopically visible alterations of the liver and spleen of the host were carried out in experimentally infected Mastomys natalensis. Following the oral administration of infective eggs the first stage larvae hatched in the caecum of fasting and fed animals after about 8 and 15 hours respectively. The prepatency could be found with 20 days. The dynamics and duration of egg production of the parasite proved to be dependent on the infective dose. After the first week of patency increasing numbers of eggs/liver were found with increasing doses of infection up to 800 eggs per animal. This relation could not be observed 76 days post infection. After infections with 50, 300 und 800 eggs per animal maximum egg production was found between 60 and 72, 36 and 48 and about 30 days p.i., respectively. The egg production of the parasites correspondently continued for more than 85 days after infection or had ceased 72 or 48 days p.i. Intraperitoneal administration of infective eggs revealed a lower infection rate, evaluated by the number of eggs per liver, than oral infection.     

Effect of UV-irradiation, spleen cells and MLN cells on protective immunity against Angiostrongylus cantonensis infection in mice

The UV-irradiated larvae of Angiostrongylus cantonensis were used for inducing immunity in mice. A single oral dose of 100 infective UV-irradiated larvae exposed for 5 min or 15 min induced 91% and 97% protection against subsequent infection. Adoptive protection against A. cantonensis could also be transferred by spleen and mesenteric lymph node cells obtained from vaccinated mice.     

Nippostrongylus brasiliensis: local humoral responses in the lungs and intestines of rats following vaccination with irradiated larvae

Groups of rats were infected with 2000 normal larvae of Nippostrongylus brasiliensis or larvae irradiated with 10 to 120 kR. On Day 10 after infection half the animals from each group were autopsied. The remainder were challenged with 5000 unirradiated larvae on Day 15 and killed ten days later. During the experiment enteric antibody levels were estimated by coproantibody measurement. At autopsy the worm burdens were determined and worm-specific antibodies evaluated in lung extracts and serum. It was found that the levels of coproantibody detected with adult worm metabolites were positively correlated with the number of adult nematodes recovered from the intestine after primary infection. The challenge induced a similar increase of these antibodies in all immunised rats which reflected a high immunity to reinfection of vaccinated animals. Preliminary immunochemical studies suggested that the coproantibodies had SIgA properties. In lung extracts of rats immunised with larvae irradiated at 40, 80, or 120 kR and in all animals after challenge, antibodies reacting with infective larval antigens were found. Their titres were negatively correlated with serum antibody levels. The significance of bronchial and enteric antibodies in conferring protection against challenge remains to be elucidated.     

Studies on the chemoprophylaxis of subperiodic Brugia malayi infection in the leaf monkey (Presbytis melalophos) with diethylcarbamazine citrate

The chemoprophylactic use of diethylcarbamazine citrate at total oral doses of 15--180 mg/kg body weight was tested against subperiodic Brugia malayi infection in the leaf monkey (Presbytis melalophos). A total dose of 45 mg/kg body weight given over 9 days killed all developing infective larvae. Similarly, a total dose of 35 mg/kg body weight given over 7 days killed all fourth stage larvae. The minimum effective dose that prevents infection would be 5 mg/kg body weight daily for 7 days every month.     

Cuticular reactivity of early larval stages of Ascaris suum: binding of fractions of immune serum to the surface of infective and parasitic stage larvae as detected by the mixed antiglobulin test.

Infective stage and early parasitic larvae of Ascaris suum were evaluated for surface reactivity with serum from uninfected and hyperimmune guinea-pigs. Cuticular binding of serum components was assessed by the mixed antiglobulin test.Ensheathed infective larvae bound both normal serum proteins and 7S protein from immune serum over the entire sheath surface. Parasitic larvae recovered at 16 and 25 h post infection (h.p.i.) were poorly reactive, and binding occurred only to sites on the head and tail regions. Larvae recovered at 48 and 72 h.p.i. were highly reactive over the entire cuticle.Host serum protein was not detectable on the surface of parasitic larvae when harvested from guineapigs after a primary infection until the larvae had been in the host for 72 h. However larvae recovered from hyperimmune animals had host serum protein detectable on the cuticle as early as 16 h.p.i.     

Action of diethylcarbamazine citrate on protective immunity in rats infected with Nippostrongylus brasiliensis

Rats made immune to Nippostrongylus brasiliensis and treated with diethylcarbamazine citrate (DEC) orally (250 mg/kg X 6) exhibited significant suppression of functional immunity. Similarly, administration of compound 48/80 (100 micrograms/rat i.p.) made the immune rats susceptible to challenge infection. Treatment of rats, with 22-day infection with compound 48/80, histamine (20 mg/rat, per os), or L-histidine (20 mg/rat, orally s.c.) did not accelerate worm expulsion. A massive complement-dependent adherence of peritoneal cells (1 X 10(8], isolated from immune DEC-treated and untreated rats, to infective larvae (L3) was observed. Likewise, heavy congregation of normal peritoneal cells to larvae was noticed when the cells were incubated with sera obtained from immune, DEC-treated or untreated rats. The rats receiving mesenteric lymph node cells (125 X 10(6) i.v.) or sera (0.5 ml or 1 ml X 3 i.p.), obtained from immune DEC-treated rats and challenged with infective larvae developed 50% more worms than those which received cells or serum from untreated immune donors. DEC appears to cause suppression of functional immunity and worm expulsion is not histamine mediated.     

Dirofilaria immitis: fate and immunogenicity of irradiated infective stage larvae in beagles

Experiments were conducted on the fate of irradiated infective larvae of Dirofilaria immitis in dogs, and on the effect of these infections on a challenge dose of nonirradiated larvae administered at a later date. Six dogs were inoculated with 200 to 296 irradiated larvae; in no case was a patent infection established. No living worm was recovered beyond 66 days. Eight dogs inoculated with 200 to 2401 irradiated larvae over varying periods of time were exposed 57 to 190 days after the final inoculation of irradiated larvae, to a challenge infection of 200 to 250 nonirradiated (normal) larvae. The results showed that the number of worms which developed to maturity in these dogs was sharply reduced compared to that in the 5 controls (dogs inoculated with normal larvae only). The most striking effect was seen in “vaccinated” dogs which were challenged 3 months or more after the final administration of irradiated larvae.     

Regulation of Haemonchus contortus populations in sheep exposed to continuous infection

Groups of sheep were infected three times weekly for 15 weeks with infective larvae of Haemonchus contortus at four rates ranging from 600 to 4800 larvae per week. At 3-weekly intervals, sheep from each group were killed for total worm counts after receiving a dose of radiolabelled larvae which enabled a direct measurement of establishment of incoming larvae during the continuing infection. Peak H. contortus burdens were reached between 6 and 9 weeks of infection, and were related to infection rate. In the groups receiving 2400 and 4800 larvae per week, worm numbers then declined rapidly and by the end of the experiment were lower than those in the groups given 600 or 1200 larvae per week. Establishment of incoming larvae was not influenced by infection rate, and declined from 45% in the first 4 weeks of infection to insignificant levels during the final 6 weeks. The proportion of incoming larvae arrested in their development increased as the infection progressed. It was concluded that H. contortus numbers were regulated by development of resistance to infection and by a loss of established worms which was related to the current rate of larval intake, and to the host's previous experience of infection.     

Possible direct effect of diethylcarbamazine on the infective larvae of Brugia pahangi

The direct action of diethylcarbamazine (DEC) on the infective larvae of Brugia pahangi was studied. The larvae were cultured in RPMI 1640 supplemented with foetal bovine serum and antibiotics for 22 days. Most of the larvae remained alive for 8 days, but survival rate of larvae decreased rapidly from day 10 onwards. The larvae did not grow in the culture system. The addition of DEC did not affect the morbidity of the larvae and no difference was observed in the morphological characteristics between the larvae cultured in the presence or absence of DEC. The infective larvae were cultured in vitro for 5 days in the presence or absence of DEC, and inoculated into jirds. The animals were necropsied at intervals, and developing larvae and adult worms were recovered. When the larvae were cultured without DEC and then inoculated subcutaneously into jirds, 29.8% of the inoculum was recovered 3-15 days, and 25% 19-22 weeks, post-inoculation. However, when the larvae were exposed to DEC in vitro and inoculated into jirds, the rate of recovery was reduced to 25% 3-15 days post-inoculation and 2% after 19-22 weeks. When the control larvae cultured in vitro were inoculated intraperitoneally into jirds, 41.3% of inoculum was recovered 3-15 days, and 42.8% 19-22 weeks, post-inoculation. Again the corresponding value for larvae exposed to DEC in vitro was reduced to 19.8% 3-15 days, and 8% 19-22 weeks, post-inoculation. It was observed that the larvae exposed to DEC in vitro were retarded in their development in jirds.(ABSTRACT TRUNCATED AT 250 WORDS)     

Passive transfer of immunity with serum in mice infected with Nematospiroides dubius: in vitro effect of immune serum on larval infectivity

Dobson C. and Cayzer C. J. R. 1982. Passive transfer of immunity with serum in mice infected with Nematospiroides dubius: in vitro effect of immune serum on larval infectivity. International Journal for Parasitology12: 413–421. Incubation of Nematospiroides dubius larvae in serum in vitro induced 15% exsheathment after 3h. Larvae incubated in immune mouse serum at 37°C for 3h lost 20% of their infectivity for mice. Immune serum from donors given 1–7 concurrent or anthelmintic abbreviated infections all depressed larval infectivity to the same extent. Larvae incubated in immune sera were protected from the effects of passively transferred immune serum in mice following infection. The effects of incubation of larvae in immune serum were prolonged into the adult stages of the parasite and were seen as stunting of worms and a reduction in the male-female sex ratio of the parasites.     

Some observations on a possible role of lung and fecal IgA antibodies in immunity of rats to Nippostrongylus brasiliensis

Factors influencing lung IgA antibody responses to Nippostrongylus brasiliensis infections and the role of lung and fecal IgA antibodies in immunity to this nematode were studied in rats. Hooded Lister rats were vaccinated subcutaneously with infective larvae radio-attenuated at 80-180 kr or with a single dose of infective larvae somatic proteins administered intravenously or intragastrically, and then challenged 14 days later with normal larvae. It was found that optimal lung IgA antibody responses depended more on the duration of the antigenic stimulation than on the quantity of antigenic material present, although a threshold amount was required. However, comparisons of lung anti-larval IgA antibody levels in rats resistant or susceptible to challenge indicated that these antibodies were not directly involved in specific host protective immunity. Levels of haemagglutinating fecal antibodies reacting with adult nematode metabolites were correlated with the numbers of adult worms recovered from the intestines following vaccination and also with the degree of resistance to reinfection. However, preincubation of adult (day 5) nematodes in media containing the IgA fraction of fecal globulins from primary infected rats did not reduce the ability of these worms to establish and survive in naive rats.     

Experimental infection with Ancylostoma caninum larvae in mice. V. Serum protein pattern during infection with various doses.

Serum protein patterns of Swiss albino mice during Ancylostoma caninum infection with varying dose levels were studied electrophoretically. There was a significant decrease in albumin associated with a corresponding increase in beta globulin in all the infected groups. Gamma globulin decreased significantly in all groups except the one infected with a challenge dose of 4000 larvae. Maximum changes occurred on day 31, 15, 9, 15 and 6 when mice were infected with 250, 500, 1000, 2000 and 4000 larvae, respectively. There was a significant negative correlation between albumin and the infective doses and a positive correlation between beta globulin and the infective doses and among the changes caused by different infective doses.     

Cross-immunity between Haemonchus contortus and Trichostrongylus colubriformis in sheep

Cross-protective immunity between the nematode parasites, Haemonchus contortus and Trichostrongylus colubriformis, was examined in sheep vaccinated with irradiated larvae of either species. Secondary immunological responsiveness stimulated in this manner protected only against challenge infection with the species used for vaccination. Significant cross-protective immunity was not observed. Titres of serum antibody to an extract of adult but not infective larval T. colubriformis reflected the specificity for protective immunity. Immediate hypersensitivity skin reactions to nematode extracts did not reflect the antigen-specificity for protective immunity.     

Effects of immunoactivity on Ascaris suum infection in mice]

The immune response to sheep red blood cell (sRBC) was monitored in the mice infected with Ascaris suum or Trichinella spiralis. The effects of the infection with T. spiralis or the injection with cyclophosphamide(CY) as an immunosuppression agent prior to challenge infection with the embryonated eggs of A. suum were monitored in mice by means of the level of infection with A. suum and cellular and humoral immune response to sRBC. Following the oral administration of 1,000 eggs of A. suum to mice, delayed-type hypersensitivity (DTH) and rosette-forming rate were gradually decreased and reached to the lowest levels at the 5th week and 6th week postinfection, respectively, and then returned to normal at the 10th week. The hemagglutinin(HA) and hemolysin(HE) titers were gradually elevated and reached to peak at the 3rd week postinfection, and then returned to normal level. The appearance ratios of the eosinophils and mast cells were in peak at the 4th week and the 2nd week postinfection, respectively. Meanwhile the harvest ratio of A. suum larvae from the liver and lungs was 21.97% at the 1st week postinfection. Following the oral administration of 300 T. spiralis infective larvae, DTH and rosette-forming rate were gradually decreased with the lapse of time and reached the lowest values in the 30th and 21st day of postinfection, and then slightly increased and transiently decreased in the 70th and 80th day of postinfection, respectively. HA and HE titers were the lowest in the 21st and 90th day, whereas the ratios of eosinophils and mast cells were the highest on the 40th and 14th day postinfection, respectively. Following the intraperitoneal injection of CY, the body weight, the spleen weight, DTH, rosette-forming ratio, HA and HE titers, the number of WBC and the ratio of the mast cell were predominantly decreased in the 5th day, and then returned to the same value of the 1st day postinjection. The ratio of eosinophils was gradually decreased following to advance of days. At the 1st, 5th and 10th days after intraperitoneal injection of CY of 400 mg/kg, a dose with 1,000 eggs of A. suum was administered orally to mice, and harvest rate of the larvae at the 7th day postadministration was 7.07% in the 1st day, 14.94% in the 5th day, 10.1% in the 10th day, 8.02% in control group. The effect of prior infection with infective larvae of T. spiralis upon immunological sequelae of a challenge infection of mice with embryonated eggs of A. suum in 30 or 70 days interval was checked.(ABSTRACT TRUNCATED AT 400 WORDS)     

Local and systemic antibody responses in gerbils following vaccination with irradiated or non-irradiated Trichostrongylus colubriformis larvae

Groups of 10 Mongolian gerbils, Meriones unguiculatus, were vaccinated with 1,500 gamma-irradiated Trichostrongylus colubriformis infective larvae (L3) or with non-irradiated larvae. 25 days later five gerbils from each group were necropsied and the remaining gerbils challenged with 1,500 non-irradiated T. colubriformis infective larvae. Systemic, local intestinal and coproantibody levels were compared in each group of gerbils 25 days after vaccination and 26 days after challenge. Strong local intestinal and faecal antibody responses were detected. Coproantibodies reflected antibody levels in the intestinal contents and in mucosal extracts. The results gave further support to the view that coproantibody measurements provide a sensitive index of immunity at mucosal surfaces to intestinal parasites.     

Observations on Toxocara pteropodis infections in mice

Infection in mice with Toxocara pteropodis was investigated. In mice fed infective eggs, third-stage larvae hatched out and penetrated the mucosa, predominantly that of the lower intestine. They travelled via the portal vein to the liver, where they remained at least 14 months. They grew in length from 430 +/- 15 micron, at three days post infection (p.i.), to 600 +/- 50 micron, at six to nine weeks p.i., after which time growth ceased. Blood eosinophilia appeared at 28 days p.i., and eosinophil levels continued to rise gradually beyond this time. In female mice the larvae did not migrate from the liver in response to pregnancy or lactation. When infective eggs were inoculated subcutaneously or intra-peritoneally, larvae hatched out and ultimately appeared in the liver in larger numbers than seen with oral infections.     

The predatory capability of three nematophagous fungi in the control of Haemonchus contortus infective larvae in ovine faeces

The effect of oral administration of three different nematode-trapping fungi, in aqueous suspension containing either Dactylaria sp. or Arthrobotrys oligospora conidia or Duddingtonia flagrans chlamydospores, on the number of Haemonchus contortus infective larvae in sheep faeces, was evaluated. The three selected species of fungi produce three-dimensional adhesive nets in the presence of nematodes. Sixteen Creole sheep were divided into four groups of four animals each. Groups 1 and 2 were orally drenched with a suspension containing 2x10(7) conidia of either A. oligospora or Dactylaria sp. Group 3, received a similar treatment, with D. flagrans chlamydospores, instead of conidia, being administered, at the same dose. Group 4 acted as control, without any fungi. Faecal samples were collected directly from the rectum of each sheep and faecal cultures were prepared and incubated at 15 and 21 days. Larvae were recovered from faecal cultures and counted. The highest reduction of the nematode population occurred in the D. flagrans group, reaching reductions of 96.3% and 91.4% in individual samplings in plates incubated for 15 and 21 days, respectively. Arthrobotrys oligospora showed moderate reductions in the faecal larval population, ranging between 25-64% at 15 days incubation. In general, Dactylaria sp., was less efficient in its trapping ability. Despite the inconsistent results with Dactylaria sp., reduction percentages of 73.4% and 80.7% were recorded in individual samplings during the first and second days, in plates incubated for 15 days. Duddingtonia flagrans, was shown to be a potential biological control agent of H. contortus infective larvae.     

The effect of Brugia pahangi infection on survival of susceptible and refractory species of the Aedes scutellaris complex

Life table statistics were used to examine the survival functions of filarial susceptible and refractory species of the Aedes scutellaris (Walker) group of mosquitoes, following infection with high and moderate doses of Brugia pahangi (Buckley & Edeson). Survivorship curves and hazard function curves were generated, and the median survival times and the proportions of mosquitoes surviving beyond the extrinsic incubation period of the parasite were determined. In the susceptible populations of Aedes polynesiensis Marks, Ae. pseudoscutellaris (Theobald) and Ae.tabu Ramalingam & Belkin a dose-response relationship was detected between parasite load and mortality. This relationship was characterized by a significant reduction in the proportions of infected female mosquitoes surviving at days 1 and 9 postinfection, reduction in the median survival times and an increase in the hazard rates as the infectious dose increased. The survival of the refractory species, Ae.alcasidi Huang and Ae.katherinensis Woodhill was not significantly affected by the infection. A positive correlation between microfilaraemia in the vertebrate host and parasite load in the susceptible mosquito populations was also observed. Regression analysis of the number of parasites recovered from susceptible mosquitoes at the time of death showed that mosquitoes at highest risk of dying harboured from 11.6 to 19.4 infective larvae when fed on a gerbil with sixty-five microfilariae per 20 microliters blood; this resulted in 34.4-40.2% mortality by day 9 postinfection. A mean number of 32.6-46.9 infective larvae was observed when these populations were exposed to a gerbil with a microfilaraemia of 150 mf/20 microliters and resulted in 72.8% to 80% mortality in these populations. Viable infective larvae were recovered from infected mosquitoes up to 50 days postinfection.     

Influence of primary infection on the population dynamics of Nematospiroides dubius after challenge infections in mice

Dobson C., Sitepu P. and Brindley P. J. 1985. Influence of primary infection on the population dynamics of Nematospiroides dubius after challenge infections in mice. International Journal for Parasitology15: 353–359. Similar proportions of the inoculum of Nematospiroides dubius larvae reached sexual maturity by 14 days after administration of 50–400 larvae but more adult worms had been expelled by day 63 after infection from those mice infected with 50 vs 400 larvae. There was a significant correlation between time and worm expulsion for all inoculum size groups except for mice given 400 larvae.In mice reinfected with 100 larvae, after termination of primary infections derived from 10 through 400 larvae, more worms from the challenging dose were recovered from mice given greater compared with those given smaller numbers of larvae at primary infection. The N. dubius population size after challenge infection was correlated positively both with number of larvae administered as the primary infection and with the resultant population size during that infection. The serum anti-N. dubius antibody titres after reinfection were higher in mice given 400 compared with those given fewer larvae at primary infection, and the fecundity and female to male sex ratio of the N. dubius populations decreased in proportion to these antibody titres.Protective immunity against challenge N. dubius infection, in mice which had been drenched free of adult worms established from 400 larvae for 5 down to 1 weeks before reinfection, increased from 45% (1 week) to 80% (5 weeks). There was a negative correlation between the population size of N. dubius during challenge infection and the duration between anthelmintic treatment and challenge infection.