Number Of Uterine Eggs Research Articles

Biological variation between two Brazilian geographical isolates of Echinostoma paraensei

The biological behaviour and morphometric data from two allopatric isolates of Echinostoma paraensei (Rio Bonito - RB and Sumidouro - SU) collected from naturally infected Nectomys squamipes from two secluded Atlantic Forest fragments were studied. Mice that had been experimentally infected with ten encysted metacercariae of each isolate were monitored weekly in two trials to analyse worm burden and the kinetics of worm distribution along the intestine. The total number of uterine eggs, wet weights and measurements of the worms and body, acetabulum, testes and ovaries were also analysed. The RB isolate showed a higher worm burden, 7.7+/-0.8, and a longer life span, 16 weeks, compared to a worm burden of 5.8+/-1.1 and life span of 9 weeks for the SU isolate. Worms of the RB isolate were clustered in the duodenum and in the bile duct while the SU isolate worms were dispersed along the small intestine of infected mice. Both isolates developed similarly as regards morphometric data and wet weight, although the total number of uterine eggs was greater in RB. The degree of intraspecific variation observed in the worm distribution along the intestine, worm burden and life span raises questions regarding the use of these criteria for species differentiation. These findings suggest that variation in biological parameters found between the E. paraensei isolates could result from geographical isolation and, in particular, the environmental conditions of transmission. Further studies on E. paraensei polulations from different forest fragments will contribute towards an understanding of the speciation of this parasite.

Effects of a 100 metacercarial cyst inoculum on the host–parasite relationship of Echinostoma caproni and ICR mice

The host-parasite relationship of a 100 metacercarial cyst inoculum of Echinostoma caproni in the ICR mouse was examined. Three groups of mice, A, B and C, each with six mice per group were used and all mice were necropsied at 14 days postinfection (p.i.), at which time the worms were ovigerous. Group A consisted of uninfected controls, whereas group B received 25 cysts per mouse (low dose) and group C received 100 cysts per mouse (high dose). There was no significant difference in food consumption between any of the groups from 0 to 14 days p.i. Control mice increased their body weight by 12%, group B by 5%, and group C showed a less than 1% increase in body weight between 0 and 14 days p.i. Echinostome parasitism caused a significant increase in the diameter of the mouse gut, with the gut of group C being more significantly dilated than that of either group A or B. The average worm recovery from group B was 20 worms per host, compared to 72 worms per host from group C. The mean wet and dry weights per worm from group B were 2.4 and 0.4 mg, respectively as compared to 0.6 and 0.2 mg respectively for group C. The mean number of uterine eggs per worm from group B was 180 compared to 125 for worms from group C. Worms from group C were more widely distributed in the small intestine than those from group B. Crowding effects associated with the high dose infection were clearly demonstrated in E. caproni from ICR mice.

Genetic difference in susceptibility and fatality of three strains of mice experimentally infected with Neodiplostomum seoulense.

The genetic influence on host susceptibility to Neodiplostomum seoulense infection and fatality of the host was studied in 3 inbred strains of mice (BALB/c [H-2d], C3H/He [H-2k], and C57BL/6 [H-2b]). The survival of the mice, worm expulsion kinetics, worm size, number of eggs produced per day (EPD), and number of uterine eggs were observed from day 1 to day 40 postinfection (PI) with 100 or 200 metacercariae per mouse. Infection with N. seoulense was highly lethal to all 3 strains of mice, but the lethality was dose-dependent and varied according to the genetic backgrounds of the mice. The C3H/He mice exhibited the highest mortality, the lowest worm burdens and EPD, and the quickest expulsion of worms. It is suggested that different genetic backgrounds of mice appear to affect the host's capacity to expel N. seoulense and the fatality of the hosts themselves.

Susceptibility of Various Species of Animals and Strains of Mice to Gymnophalloides seoi Infection and the Effects of Immunosuppression in C3H/HeN Mice

Susceptibility to Gymnophalloides seoi infection was studied in 8 species of animals, including 7 strains of mice; the effects of immunosuppression on susceptibility were examined in C3H/HeN mice. One hundred metacercariae of G. seoi isolated from naturally infected oysters were orally administered to each animal. Worm recovery rate (WRR), worm dimensions, and the number of uterine eggs were obtained at day 3 and day 7 postinfection (PI). Average WRR from gerbils, hamsters, and cats at day 7 PI was 28.0%, 14.2%, and 10.9%, respectively, the former 2 figures of which were significantly higher than the rate of 0.0-4.0% from Sprague-Dawley rats, dogs, ducks, guinea pigs, and chicks. In the case of mice, average WRR at day 7 PI was 12.4% (KK strain), 11.8% (C3H/HeN), 9.6% (ICR), 6.4% (BALB/c), and 6.3% (ddY), respectively; the first 3 figures were significantly higher than the rates from other strains, which were 1.8% (A) and 0% (C57BL/6). At day 3 PI, WRR was much higher in all strains except C57BL/6. Worm maturation was the highest in C3H/HeN mice. Immunosuppression of C3H/HeN mice by injecting prednisolone for 7, 14, or 21 days prior to infection increased WRR at day 7 PI to 27.8%, 33.8%, or 67.5%, respectively. The results show that gerbils, hamsters, cats, and KK, C3H/HeN, ICR. BALB/c, and ddY mice are laboratory hosts that are fairly susceptible to G. seoi infection. In C3H/HeN mice, susceptibility was markedly enhanced by immunosuppression.

Passive Transfer of Immune Serum Reduces the L1/Adult Ratio of Worms Recovered from the Intestines of Strongyloides stercoralis-Infected Gerbils

In Strongyloides stercoralis-infected gerbils it had been observed previously that the ratio of first-stage larvae to adult worms decreases after 3 wk of infection. Serum obtained from gerbils after this decrease in fecundity, but before worms were expelled, was transferred passively to other infected gerbils during the peak of worm fecundity. The immune serum caused a significant decrease in the L1/adult ratio but had no effect on the number of uterine eggs, the length, or the intestinal and ovarian ultrastructure of adult worms. Apparently a factor(s) in the immune serum either killed eggs, after oviposition, or the hatched larvae, without damaging the adult worms.

Effects of gamma-irradiation on the survival and development of Gymnophalloides seoi in C3H mice.

An experimental study was carried out to observe the effects of radiation on the infectivity of metacercariae of Gymnophalloides seoi to C3H mice. Oysters, the second intermediate host, were collected from an endemic area, and non-irradiated control, metacercaria-irradiation, and oyster-irradiation groups were prepared. One hundred metacercariae were infected orally to each mouse, and worm recovery rate was compared by groups at 7th day post-infection. In the metacercaria-irradiation group, the worm recovery rate was significantly reduced at radiation doses higher than 200 Gy, and the number of intrauterine eggs significantly reduced at doses over 50 Gy. In the oyster-irradiation group, 50 Gy significantly reduced both the worm recovery rate and number of uterine eggs. In the two groups, no worm was recovered at 1,000 Gy irradiation. Conclusively, irradiation of oysters with 200-1,000 Gy was effective to control infectivity of metacercariae to C3H mice, and could be adopted as a control measure for gymnophalloidiasis.

Interspecific and Intraspecific Competition among Pinworms in the Hindgut of Periplaneta americana

To determine the relative importance of inter- and intraspecific factors in regulating number and fecundity of pinworms in the hindgut of Periplaneta americana, repeated samples of roaches, each consisting of an adult male, an adult female, a late instar, and an early instar, were collected from each of 2 colonies, 1 colony (mixed) infected with Thelastoma sp., Hammerschmidtiella diesingi, and Leidynema appendiculatum and the other (isolate) infected with only the last-named species. Roaches were dissected, volume of hindgut estimated, and the number of female worms of each species was recorded. Female worms were dissected and the number of uterine eggs was counted. Gut volume was a significant predictor of numbers of all species except H. diesingi, numbers of which were correlated positively with those of its 2 interspecific associates. There was little evidence of interspecific competition within the host. In the mixed colony, L. appendiculatum occurred with Thelastoma sp. less often than expected, but this was the only negative interspecific interaction observed. Fecundity was not significantly correlated with numbers of interspecifics but was strongly and negatively cor- related with numbers of intraspecifics in all species. Leidynema appendiculatum occurred at about the same intensity in isolate and mixed colonies. These results suggest that the number of each species is independently regulated. Typically this occurs through nonoverlapping niches, but all evidence points to there being broad niche overlap in the species. Unpublished findings suggest that L. appendiculatum and Thelastoma sp. limit their own numbers by intraspecific interference, a phenomenon reported in several other pinworms. Reduced fecundity is presumably a sublethal manifestation of this interference. We propose that intraspecific interference holds numbers of each species below carrying capacity and permits their coexistence despite broad niche overlap. Prevalence was below 50% in the mixed colony and was 100% in the isolate colony. This suggests that the community in the mixed colony is the result of a 2-stage process where interspecific effects play an important role in establishment of a species but where intraspecific effects dominate the in-host environment.

Increase of rate of egg production with growth in some intestinal nematodes of sheep and horses

Ractliffe L. H. & LeJambre L. F. 1971. Increase of rate of egg production with growth in some intestinal nematodes of sheep and horses. International Journal for Parasitology, 1: 153–156. There is a positive relationship between the number of uterine eggs and size of worm in Chabertia ovina, Haemonchus contortus, Oesophagostomum columbianum, and Para-scaris equorum, and a linear relationship between the weight of the egg sac and the weight of the remainder of the worm in Oxyuris equi. These relationships imply that the rate of egg production increases with growth. Consequently it would be expected that (a) the total egg output of a population of parasites would be more closely related to the total weight of the worms than to their number and (b) there would be a logarithmic increase with time in the egg output of a newly infected host even if the increase in the number of worms harbored by the host were only linear with time.