Helminth Parasites of Conventionally Maintained Laboratory Mice: II- Inbred Strains with an Adaptation of the Anal Swab Technique

Abstract

Worm burdens recovered from inbred mice strains, namely C57Bl/6, C57Bl/10, CBA, BALB/c, DBA/ 2 and C3H/He, conventionally This approach intends to add new data on the helminth parasites of laboratory mice, since these investigations have arised a great interest and also, taking into account that these hosts as experimental animal models, are widely utilized in the evaluation of several biological parameters. Previously, besides the considered Swiss Webster mice, only two inbred strains (C57Bl/6, DBA/2) were investigated for the presence of helminths in Brazil (Pinto et al. 1994).Thus, the present findings ratify those reported for these strains, as well as complement the evaluation of worm burden in the other commonly referred inbred mice.The modification of the anal swab technique proposed herein aims to avoid unnecessary necropsies to investigate the spectrum of intestinal parasites in a rodent colony, since oxyurid eggs are of difficult detection during conventional stool examination procedures. MATERIALS AND METHODSTwo hundred and fifty Mus musculus (Linnaeus, 1758) inbred mice from two animal houses in the State of Rio de Janeiro, RJ, Brazil, were divided in two groups (A, B) according to their source. The suppliers were not identified by name due to ethical reasons. In group A, were included mice of the strains C57Bl/6, C57Bl/10, CBA, BALB/c, DBA/2 and C3H/He, with 25 animals each. The group B was represented by the strains C57Bl/6, CBA, BALB/c and C3H/He, with 25 mice each. Mice were male, 30 days old, weighting 20g each.Mice were sacrificed, helminths were recovered and processed for study as described elsewhere (Pinto et al. 1994).As for the swab anal procedures, the technique of Hall (1937) was modified and the device consists of a plastic rod (Fig. 1), with appropriate dimensions, for the examination of mice weighting at least 18g. One hundred and twelve mice were tested by this method. Animals are maintained in the proper position (Hofman's position), in order to avoid stress to the animals during the procedure. The rod is moistened in a 0.85% NaCl solution (Fig. 2) and after, introduced into the anus of the mouse, with carefully induced rotatory movements (Fig. 3), to avoid bleeding. The collected feces sample is transferred to a drop (20 µl) of saline physiological solution (0.85% NaCl) on a slide with a coverslip and examined under light microscope.

Patterns of infection with the nematodes Syphacia obvelata and Aspiculuris tetraptera in conventionally maintained laboratory mice

“…Panter (1969) and Taffs (1976) reinforce the acquired resistance to infection between the 4th The high frequency of S. obvelata in comparison with A. tetraptera worm burdens presently observed is not in accordance with Rosas (1977) that reports higher frequencies of the latter species; nevertheless, this high frequency of S. obvelata in rodent colonies is justified considering the nematode life-cycle, that is shorter in this species, thus inducing the infection in a larger number of mice in short periods (Flynn 1973, Jacoby & Fox 1984, Scott & Gibbs 1986, Coghlan et al 1993, Moulia et al 1993, Klement et al 1996, Zenner 1998. Gonçalves et al (1998) observed associations of S. obvelata and A. tetraptera in outbred and inbred mice; this parameter is to be analyzed with basis on the population dynamics of pinworms in mice, as previously reported (Scott & Gibbs 1986). Hayunga (1991) and Gonçalves et al (1998) agree in the statement that associations of different helminth species in a same host specimen induce the establishment of competition for nutrients and overgrowth of the parasites; however, according to Scott and Gibbs (1986) this competition is not related to the habitat since the site of infection of S. obvelata is the cecum, while A. tetraptera is recovered mainly from the colon; thus, this factor is not to be considered as the principal in these associations.…”

“…The improvement of laboratory animals either considering genetic approaches in the utilization of homogeneous strains or on the basis of sanitary conditions in an attempt to maintain these animals free from pathogens is a priority, since undetected autochthonous parasitic infections in laboratory animals, even in the absence of clinical signs, may act as variables, during experimental assays (Eaton 1972, Saiz-Moreno et al 1983, Jacoby & Fox 1984, Huerkamp 1993, Pinto et al 1994, Sato et al 1995, Rehbinder et al 1996, Rosas 1997, Gonçalves et al 1998, Ortiz et al 2000. In conventional animal facilities, rodent colonies are frequently infected with helminths or become infected in the laboratories where they are mantained in the course of experiments.…”

“…Gonçalves et al (1998) observed associations of S. obvelata and A. tetraptera in outbred and inbred mice; this parameter is to be analyzed with basis on the population dynamics of pinworms in mice, as previously reported (Scott & Gibbs 1986). Hayunga (1991) and Gonçalves et al (1998) agree in the statement that associations of different helminth species in a same host specimen induce the establishment of competition for nutrients and overgrowth of the parasites; however, according to Scott and Gibbs (1986) this competition is not related to the habitat since the site of infection of S. obvelata is the cecum, while A. tetraptera is recovered mainly from the colon; thus, this factor is not to be considered as the principal in these associations.…”

“…In conventional, semi-open facilities, rodent colonies are frequently infected with helminths. These parasites, if undetected, can interfere in the development of protocols and alter the interpretation of final results (Pinto et al 1994, Gonzalez 1996, Luca et al 1996, Gonçalves et al 1998. The analysis of different biological parameters related to the presence of nematodes in mice conventionally kept in animal houses in which sanitary conditions and barriers have not been properly controlled, is presented.…”

Worm burdens in outbred and inbred laboratory rats with morphometric data on Syphacia muris (Yamaguti, 1935) Yamaguti, 1941 (Nematoda, Oxyuroidea)

“…In Brazil, complete reports related to helminths parasitizing outbred and inbred laboratory mice are those of Pinto et al (1994), when parasites were identified, described, illustrated, worm burden quantified and prevalences established for Swiss Webster, C57Bl/6 and DBA/2 strains, with a further proposition of an adaptation of the anal swab technique for the detection of oxyurid infections in C57Bl/6, C57Bl/10, CBA, BALB/c, DBA/2 and C3H/He mice (Gonçalves et al 1998).…”