versão On-line ISSN 0717-7712
Parasitol. latinoam. v.62 n.3-4 Santiago dez. 2007
Parasitol Latinoam 62:165 -169, 2007 FLAP
ARTÍCULO DE ACTUALIZACIÓN
The community of gastrointestinal helminths in the housemouse, Mus musculus, in Santiago, Chile.
CARLOS A. LANDAELA-AQUEVEQUE*, MARÍA D. R. ROBLES** and PEDRO E. CALLAN*
* Departamento de Ciencias Biológicas Animales, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile.
The house mouse, Mus musculus, has been present in Chile since approximately 1600 AD and it is the most tipically synanthropic rodent in Chile. In order to know its parasites a survey was conducted in three different localities in Santiago. The helminthes community was poor in species and only three nematodes species were found: Syphacia obvelata,Aspiculuris tetraptera and Physaloptera calnuensl All these species constitutes the first record in Chile. This is also the first record of P. calnuensis in this host. Syphacia obvelata was the most abundant and the most prevalent.
Key words: Syphacia, Aspiculuris, Physaloptera,Mus musculus.
El ratón doméstico, Mus musculus, está en Chile desde aproximadamente el 1600 DC. y es el más sinantrópico de los roedores chilenos. Para conocer sus parásitos se realizó un estudio en tres diferentes localidades de Santiago. La comunidad de helmintos fue pobre en especies y sólo se encontraron tres especies de helmintos: Syphacia obvelata, Aspiculuris tetraptera y Physaloptera calnuensis; todas estas especies constituyen el primer registro para Chile. Esté es también el primer hallazgo de P. calnuensis en este hospedador. Syphacia obvelata fue la especie más prevalente y abundante.
Mus musculus, Linaeus, 1758 is a wordwide distributed rodent. This mouse first settled in Chile approximately four centuries ago1. It is found in both urban and suburban enviroments, and it is the most tipically synanthropic rodent in Chile2. Currently, most of our knowledge about its parasites is limited to lists compiled from regions outside of the American continent3,4. Moreover, they have been made without ecological data or morphometric comparisons5,6. Herein we report the first record of gastrointestinal helminths of M. musculus in Chile and add data of parasite distribution in thee localities of Santiago, Chile.
MATERIALS AND METHODS
The survey were conducted between March and October of 2002 in Santiago, Chile. 88 mice were live-trapped using Sherman traps baited with rolled oats at each of the three localities: 1) Facultad de Ciencias Veterinarias y Pecuarias (FAVET) of the Universidad de Chile (39 individuals) (33° 34' 20" S; 70° 37' 51" E; 620 mas1.); 2) Fundo El Bosque (28) (33° 32' «50 S: 70° 48' 10" E; 454 mas1); and 3) Pudahuel (21) (33° 26' 10" S; 70° 49' 20°; 464 mas1).
The mice were killed using ether. Helminths were collected, fixed in 10% formalin and preserved in 70% ethanol, cleared in lactophenol, and studied under a light microscope. The prevalence (P), mean intensity (MI) and mean abundance (MA) were calculated for each locality and species found following Bush et al.7 (Table 1). Tables 2 - 4 list measurements of the specimens, including the mean and standard deviation, followed by the range in parentheses, and those given by previous authors. All measurements are in micrometers unless otherwise stated.
Community diversity (H) and homogeneity (J) were estimated using the Shannon-Wiener index. In keeping with Rózsa8, the Kruskal Wallis non-parametric ANOVA was used to compare mean abundances and mean intensities of helminths in each localities. The test of hypothesis of independence (Chi square) was used to compare prevalences of helminths in each localities. Specimens of helminths were deposited in the Museo Nacional De Historia Natural. Santiago, Chile (P. calnuensis: MNHN1537. MNHN1542, MNHN1543; S. obvelata: MNHN1538; A. tetráptera: MNHN1539. MNHN1540, MNHN1541)
A total of 2.405 specimens were collected and identified as three different species: Physaloptera calnuensis Sutton, 1989, Aspiculuris tetr áptera (Nitzch, 1821) Schulz, 1927 and Syphacia obvelata (Rudolphi, 1802) Seurat, 1916. These species were recovered from 2 infestation sites: stomach (P. calnuensis) and caecum-colon (A. tetraptera, S. obvelata).
Syphacia obvelata was found in the 3 localities, while A. tetraptera and P. calnuensis were found in 2, the first one in FAVET and Pudahuel, and the second in FAVET and Fundo El Bosque (Table 1).
In Chile, species of genus Physaloptera have been found in humans, dogs and cats9,10, in the form of eggs in feces. There is no study of adult worms. P. calnuensis was originally described from Calomys laucha Fischer 1814 (Cricetidae) in Artigas, Uruguay11. This paper represents the first record of this species in M. musculus, and in Chile. The only discripancie found between both hosts was the tail length. This difference is related to the different hosts and areas (Table 2).
Both A. tetraptera and S. obvelata have been found in M. musculus in the laboratory and in the wild1,12,13.
Aspiculuris tetraptera has previously been recorded in laboratory mice from South American countries1416. Other species oí Aspiculuris found in the American continent was assigned to A. lahorica Akhtar, 1955 in house mice of Mexico17. Measurements of this worm are similar to those given for A. tetraptera (Table 3). However, the number of caudal papillae is distinct 10 versus 14, respectively18.
Eleven species ofí Syphacia have been recorded in America, included S, obvelata14,16,19,20. However, among them, only one species, S. phyllotios has been recovered in Chile from Phyllotis darwini Waterhouse, 183728. Therefore S. obvelata is the second report of this genus and the first of this species in Chile. Measurements of S. obvelata in this paper are similar to those given by previous authors14,21,22 (Table 4).
Syphacia obvelata was the species with highest values of P, IM and AM (Table 1). There were not significant differences in the prevalence, mean intensity and mean abundance between sites either within parasite species neither at the component community level. (Table 1). Pudahuel was the site with the highest diversity and homogeneity (Table 5).
The low richness of parasite communities in this study is notable. In contrast, in M. musculus from Mexico, a component community of 6 different species was found17. However, a study carried out on several Chilean rodent species23, showed that in Chile the low parasitic richness is not an uncommon result. This case was also observed in studies on invasive species of Chile such as hares (Lepus europaeus Pallas, 1778) and rabbits (Oryctolagus cuniculus Linaeus, 1758)2425. This could be due to extrinsic factors such as a lack of vectors or intermediate hosts; the possibility that the invasive mouse could have shed its parasites in the process of colonization2627; or due to geographic barriers for colonizations (such as The Andes Mountains or the Atacama Desert) which make Chile similar to an island. Low parasite richness is frequent in introduced hosts in island as occurs in Southern Indian Ocean and in Formentera (Balearic) island1213. Future studies will clarify the effect of these factors on the richness of parasites in Chilean rodents.
This is the first research of gastrointestinal helminth fauna of the M. musculus in Chile, and it also provides a new host and locality record.
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Acknowledgements :The authors wish to sincerely thank Dra. GracielaNavone, CEPAVE, Argentina, for assisting in the identification of parasite species. The authors also would like to thank Dra. Griselda Pulido and Dra. Eileen Harris for kindly providing of references of Aspiculuris. Funding provided by the Project of United Nation for the Development (PNUD) CHI99003 - 20010452 is also gratefully acknowledged.
Pedro E. Cattan.