Morphological and molecular identification of hymenolepidid cestodes in children and synanthropic rodents from rural Mexico

Hymenolepidid cestodes of synanthropic rodents represent a risk for public health. In order to describe the occurrence of hymenolepidids in children and the role of rodents as a potential source of infection, we conducted a morphological and molecular survey on cestodes in two rural villages from Yucatan, Mexico. One hundred and thirty-five stool samples from children (64 from Paraíso and 71 from Xkalakdzonot), 233 Mus musculus (159 from Paraíso and 74 from Xkalakdzonot) and 125 Rattus rattus (7 from Paraíso and 118 from Xkalakdzonot) were analyzed for the presence of cestodes. Three hymenolepidid species were identified morphologically: Hymenolepis nana in 7.8% of children from Paraíso, Hymenolepis microstoma in 4.4% of M. musculus from Paraíso and Hymenolepis diminuta in 15.3% of R. rattus from Xkalakdzonot. The molecular characterization and phylogenetic analysis based on mitochondrial cytochrome c subunit 1 (CO1) gene and ribosomal internal transcribed spacer 1 (ITS1) region, confirmed the identity of the three cestodes isolated from Yucatan. Phylogeny of the CO1 gene identified intraspecific genetic differences within H. nana ranging from 0 to 5%, in H. microstoma from 0 to 0.4%, and in H. diminuta ranged from 0 to 6.5% which suggests, the presence of complex species within H. nana and H. diminuta infecting humans and rodents, as reported by other authors. Based on the morphological and molecular results, and the epidemiological evidence, infections with H. nana suggest a non-zoonotic transmission; however, the presence of H. microstoma and H. diminuta in synanthropic rodents serve as a possible source for human infection.     

Observations on commensal rats and their status to plague in Bombay

The distribution pattern of various types of commensal rodents in Bombay city reveals that Bandicota bengalensis constitutes the predominant commensal rodent species followed by R. rattus and Rattus norvegicus. Apart from these three types, Bandicota indica, M. musculus and an insectivore (Suncus murinus) are the three species of commensal small mammals that are frequently encountered in or near human habitations. These small mammals are prevalent throughout the year and their percentage distribution varies very little during different months of the year. None of the rodent species examined during the years 1976-85 revealed presence of Y. pestis infection by bacteriological or serological methods. From these findings, it could be concluded that in the city of Bombay a focus of zoonotic plague infection does not exist.     

A survey of Neospora caninum and Toxoplasma gondii infection in urban rodents from Brazil

Toxoplasma gondii is a protozoan parasite that infects humans and other warm-blooded animals; it uses feral and domestic cats as the definitive hosts. Neospora caninum is a protozoan parasite of animals whose life cycle is very similar to T. gondii but uses canids as definitive hosts. Small rodents play an important role in the life cycle of T. gondii , and a few findings indicated that they may be natural intermediate hosts for N. caninum . The present study was aimed at identifying infections by T. gondii and N. caninum in urban rodents. Infections by T. gondii were quantified using isolation of the parasite by bioassay in mice; molecular methods were also used for both parasites. Overall, 217 rodents were captured. Brain and heart tissues of all rodents were bioassayed in mice for the detection of T. gondii infection. Brain and heart tissues of 121 rodents had the DNA extracted for molecular analysis. Toxoplasma gondii was isolated by bioassay from a single rodent. From the 121 rodents tested for the presence of T. gondii DNA, 2 animals were positive. In contrast, DNA of N. caninum was not detected in any of the samples. In conclusion, the surveys of N. caninum and T. gondii infection in Rattus rattus , Rattus norvegicus , and Mus musculus captured in urban areas of S?o Paulo reveal a striking low frequency of occurrence of these infections.     

Retention of Leishmania (Leishmania) mexicana in naturally infected rodents from the State of Campeche, Mexico

In the State of Campeche, Mexico, zoonotic cutaneous leishmaniasis is mainly due to Leishmania (L.) mexicana. The parasite population is maintained in a mammalian species, a reservoir in which the ideal course of infection should be long and relatively nonpathogenic. The objective of the present study was to document the retention of L. (L.) mexicana in 29 naturally infected rodents. These cricetids lived in captivity for up to two years and were tested monthly for the presence of the parasite, by cultures of needle aspirates from the base of the tail. Peromyscus yucatanicus and Ototylomys phyllotis were incriminated as the primary reservoir hosts. The finding that the multiplication of parasites in P. yucatanicus might be triggered by temperature, suggests that this animal would be a good choice for further research on L. (L.) mexicana.     

Seasonal patterns of rodents, fleas and plague status in the Western Usambara Mountains, Tanzania

Field and commensal rodents were live-trapped at three villages in an active focus of plague (Yersinia pseudotuberculosis pestis) in Lushoto District, Western Usambara Mountains, Tanga Region, Tanzania, from December 1983 to November 1984. Their flea ectoparasites were collected, identified and counted. The rodent carcasses were serologically examined for specific plague antibodies and antigens, and bacteriologically examined for bipolar staining bacilli. A total of 1758 traps were set during the 12-month period and 924 animals were caught. From these, 1037 fleas were collected. Rattus rattus (L.), Praomys natalensis (Smith) and Lophuromys flavopunctatus Thomas comprised the largest proportions of the rodent population, while Dinopsyllus lypusus Jordan & Rothschild, Ctenophthalmus calceatus Waterston and Xenopsylla brasiliensis (Baker) were the dominant flea species. Rodents were most abundantly trapped during December and January. Flea indices were highest from December to May. Human plague was most active from November to March. Rodents contained plague antibodies every month except May and July, with a peak in September. Plague antigens and bipolar bacilli were detected in rodent organs during January-April. From the product of abundance and infection rate, the most prevalent rodent hosts of plague appeared to be R. rattus, Otomys angoniensis Wroughton, P. natalensis and Pelomys fallax (Peters). Continuous integrated control of rodents and fleas was recommended, reinforced by quarantine and maintenance of a surveillance service for clinical detection, diagnosis and treatment of patients in the plague endemic area.     

Serologic evidence of a Rickettsia akari-like infection among wild-caught rodents in Orange County and humans in Los Angeles County, California.

We detected antibodies reactive with Rickettsia akari, the etiologic agent of rickettsialpox in humans and in 83 of 359 (23%) rodents belonging to several species, collected in Orange County, CA. Reciprocal antibody titers >1:16 to R. akari were detected in native mice and rats (Peromyscus maniculatus, P. eremicus, and Neotoma fuscipes) and in Old World mice and rats (Mus musculus, Rattus rattus, and R. norvegicus), representing the first time that antibodies reactive with this agent have been detected in four of these species and the first report of these antibodies in rodents and humans west of the Mississippi River. We then tested serum samples from individuals who used a free clinic in downtown Los Angeles and found that 25 of 299 (8%) of these individuals had antibody titers >1:64 to R. akari. Serologic evidence suggested that R. akari or a closely related rickettsia is prevalent among several rodent species at these localities and that infection spills over into certain segments of the human population. Isolation or molecular confirmation of the agent is needed to conclusively state that R. akari is the etiologic agent infecting these rodents.     

Antibodies to lymphocytic choriomeningitis virus in wild rodent sera in Egypt

Specific antibodies to lymphocytic choriomeningitis (LCM) virus were detected in sera of wild rodents trapped in different regions of Egypt. The highest proportion of positive sera (11.5%) was found in Sinaa Governorate of the Asian Continent, followed by Sharkia Governorate (5.6%) adjacent to Sinaa and Giza Governorate (1.8%). In Upper Egypt, however all 610 rodent sera collected in Aswan, Red sea Pernees and New Valley adjacent to Sudan were negative. The highest percentage of positive sera was in Rattus rattus frugivorus and Mus musculus species.     

Helminths from introduced small mammals on Kerguelen, Crozet, and Amsterdam Islands (southern Indian Ocean).

Four monoxenous nematodes and 1 heteroxenous cestode were found in 4 species of introduced small mammals on isolated sub-Antarctic islands of the Indian Ocean. In the Kerguelen Archipelago, Syphacia obvelata, Passalurus ambiguus (Nematoda: Oxyuridae), and Rodentolepis straminea (Cestoda: Cyclophyllidae) were respectively found in the house mouse Mus musculus, the rabbit Oryctolagus cuniculus, and the black rat Rattus rattus. One accidental nematode, Trichostrongylus sp. (Nematoda: Trichostrongylidae), was also found in a black rat on Kerguelen. On Possession Island (Crozet Archipelago), R. straminea was present in the black rat. On Amsterdam Island, the brown rat R. norvegicus harbored 2 species, R. straminea and Nippostrongylus brasiliensis (Nematoda: Heligmonellidae). The small number of founder hosts and the depauperate terrestrial communities on these remote islands explain the low diversity in the helminth communities of these introduced mammals compared with continental populations.     

Anisakid nematodes from stranded pygmy sperm whales, Kogia breviceps (Kogiidae), in three localities of the Yucatan Peninsula, Mexico

The present paper reports the presence of 3 adult and juvenile anisakid nematode species: Anisakis simplex, A. brevispiculata, and Pseudoterranova ceticola, which were recovered from the digestive tract of stranded pygmy sperm whales (Kogia breviceps) from 3 localities along the coast of the Yucatan Peninsula. The presence of these anisakid adult nematodes suggests that larval stages may occur in cephalopods or fishes used for human consumption, which represents a potential danger to public health. The occurrence of the 3 anisakid species in coastal waters of the Yucatan Peninsula represents new geographical records for Mexico.     

Isolation of members of the Haemophilus-Pasteurella-Actinobacillus group from feral rodents

46 feral rodents, including a common vole (Microtus arvalis), house mice (Mus musculus), muskrats (ondatra zibetica), house rats (Rattus rattus) and brown rats (R. norvegicus) were examined for bacteria of the Haemophilus-Pasteurella-Actinobacillus group. Haemophilus spp. (only M. musculus examined) were not obtained. All animal species were found contaminated by P. pneumotropica and/or Actinobacillus spp. Almost all M. musculus (96%) and most Rattus spp. (76%) were contaminated by P. pneumotropica and/or Actinobacillus spp. These bacteria were obtained most frequently from the upper respiratory tract, to a lesser extent from the lung and rarely from caecal contents. It is concluded that feral rodents might constitute an important source of contamination of laboratory rodents by members of the HPA-group.     

The potential role of rodents in the enzootic cycle of Rift Valley fever virus in Senegal

Wild rodents (214) of fourteen species were trapped at seven sites in Senegal. Arvicanthis niloticus and Mastomys erythroleucus were among the most frequently collected species (77.2% of total capture). All rodents were examined for the presence of anti-Rift Valley fever virus (RVFV) antibody; the prevalence over all sampled species was 3.8%, varying widely with respect to species and location. Four of 14 species of rodents were found to have anti-RVFV antibodies: Rattus rattus (one positive of two tested) Mastomys huberti (13.5%), A. niloticus (4.3%), and M. erthroleucus (2.4%). The highest prevalence of anti-RVFV antibody was recorded within the enzootic area of the Senegal River delta, at Richard Toll (9.6%). A. niloticus and M. erythroleucus and a strain of laboratory-bred mice were experimentally inoculated with two strains of RVFV and examined for viremia, illness, seroconversion and mortality. A. niloticus and M. erythroleucus demonstrated a limited resistance to infection, thus potentially allowing for the replication of virus in these animals and making these species possible candidates as hosts in the maintenance cycle of RVFV in nature.     

Bioecology of the parasites of high altitude homeothermic host-parasite systems. II. Infections by strobilocerci of Hydatigera balaniceps (Hall), H. laticollis (Rudolphi) and H. parva (Baer) in relation to sex, size and weight of Indian house rat

The influence of sex, size and weight of the Indian house rat (Rattus rattus) on concurrent liver infections with Hydatigera balaniceps (Hall), H. laticollis (Rudolphi) and H. parva (Baer) has been discussed. A significant inverse relationship was recorded between cestode infection and rat size. Parasitization index and mean worm burden-host weight ratio decreased with increase in rodent weight.     

Hantavirus-specific antibodies in rodents and humans living in Kuwait

Hantaviruses are found in widely scattered areas of the world and are transmitted by inhalation of virus-contaminated aerosols of rodent excreta. The present study was undertaken in Kuwait to investigate the serological evidence for hantavirus infection in rodents and humans. Sera were collected from 283 wild rodents and 183 human subjects (46 Kuwaitis and 137 non-Kuwaitis). The rodent sera were investigated for the presence of antibodies against the Seoul and Puumala strains of the hantaviruses by enzyme-linked immunosorbent assay and immunofluorescence technique using the virus-infected Vero E6 cells. The findings showed the presence of anti-hantavirus antibodies in seven out of the 283 (2.8%) rodents. Antibodies against the Seoul strain were present in six (2.1%) and against the Puumala strain in three (1%) rodents. Further, it was observed that three out of 84 (3.6%) of the Rattus norvegicus and four out of 174 (2.3%) Mus musculus had anti-hantavirus antibodies. Two rodents belonging to species Mus musculus had antibodies against both strains of the hantaviruses. Out of 183 human sera, 13 (7%) were positive for hantavirus antibodies. Among the Kuwaitis 5/46 (11%) and among the non-Kuwaitis 8/137 (6%) were positive for the hantavirus antibodies. Antibodies to both Puumala and Hantaan strains were detected in Kuwaitis as well as in non-Kuwaitis. Although no human case of hantavirus illness has yet been reported in Kuwait, the serological evidence of infection suggests a constant vigil.     

Use of monoclonal antibodies for the identification of Leishmania spp. isolated from humans and wild rodents in the State of Campeche, Mexico.

The genus Leishmania includes 30 described species which infect a wide variety of mammalian hosts. The precise identification of leishmanial parasites at the species level is very important in order to determine whether an organism, causing the disease in a given area, is of the same biotype as that found in suspected mammalian reservoirs. The objectives of the present study were (1) to identify leishmanial parasites isolated from humans and wild rodents from the State of Campeche, an endemic focus of localized cutaneous leishmaniasis (LCL) in southern Mexico, using an indirect immunofluorescent assay (IFA) with monoclonal antibodies (Mabs); and (2) to determine if the parasites of the two types of hosts were of the same biotype. All the wild rodents (six Ototylomys phyllotis, eight Oryzomys melanotis, five Peromyscus yucatanicus and two Sigmodon hispidus) and 96% (24/25) of the human isolates were identified as Leishmania (L.) mexicana confirming that this specific LCL focus is a wild zoonosis. The presence of one human isolate of L. (Viannia) braziliensis in the State of Campeche, confirmed the importance of an accurate taxonomic identification at species level.     

Eimeviu (Protozoa: Coccidia) in wild populations of some British rodents

Four species of wild rodents from the British Isles, Myocustor coypus (the Coypu), Apodemus sylvaticus (the Wood mouse). Mus musculus (the House mouse) and Clethrionomys glureolus (the Bank vole) were examined during 1918 and 1919 for the presence of coccidian parasites of the genus Eimeriu. From an examination of 852 faecal samples a total of 14 species of Eimeriu was found. Species identification was based mainly on the morphology of the sporulated oocyst. The number of host species examined and the overall prevalence of infection were as follows: 252 M. coypus (45·6% infected), 471 A. sylvaticus 56·5%), 59 M. musculus (42·4%) and 70 C. glureolus (22·9%). The results are compared with previous surveys and discussed in the light of the general knowledge concerning coccidial infections. The present work showed that prevalence of infection in the wild rodents studied may be influenced by the age, weight and sex of the host, and by season.     

Population-Dynamics and Diet of Rodents on Rangitoto Island, New Zealand, Including the Effect of a 1080 Poison Operation

The objective of this study was to quantify the population dynamics, morphological characteristics, and diet of rodents on Rangitoto Island (Hauraki Gulf, New Zealand) to provide information for the future development of an eradication strategy. An aerial 1080 operation to eradicate possums and wallabies was carried out two months after the study began. The effects of this operation on rodent population dynamics are discussed. Both ship rats (Rattus rattus) and mice (Mus musculus) were trapped on Rangitoto Island over a 15 month period. A two month decline in mouse abundance was noticed following poisoning; following this the population recovered rapidly, reaching a Peak of 12 captures per hundred trap nights (12 C100TN(-l)) in autumn and then declining over winter. A longer decline in ship rat abundance was observed, although this reached a pre-poisoning level of 1.6 C100TN(-l) in April. Thereafter the population did not reach pre-poisoning levels again. Total body length and weight were significantly related to age, and were similar to those of mice and ship rats recorded in other New Zealand studies. The majority of breeding appeared to occur between September and May for both species. There was evidence of delayed reproductive maturity for female mice and mts born at the end of summer. A relatively large number of young mice were caught in autumn, with very few being caught in spring. Invertebrates were the major component of both species' diet, with weta (Hemideina thoracica) predominant, while plant matter was a minor constituent. The nematodes Physoloptera getula and Mastophorus muris were present in the stomachs of 22% of mice and 59% of ship rats.     

cDNA nucleotide sequence encoding the ZPC protein of Australian hydromyine rodents: a novel sequence of the putative sperm-combining site within the family Muridae

This comparative study of the cDNA sequence of the zona pellucida C (ZPC) glycoprotein in murid rodents focuses on the nucleotide and amino acid sequence of the putative sperm-combining site. We ask the question: Has divergence evolved in the nucleotide sequence of ZPC in the murid rodents of Australia? Using RT-PCR and (RACE) PCR, the complete cDNA coding region of ZPC in the Australian hydromyine rodents Notomys alexis and Pseudomys australis, and a partial cDNA sequence from a third hydromyine rodent, Hydromys chrysogaster, has been determined. Comparison between the cDNA sequences of the hydromyine rodents reveals that the level of amino acid sequence identity between N. alexis and P. australis is 96%, whereas that between the two species of hydromyine rodents and M. musculus and R. norvegicus is 88% and 87% respectively. Despite being reproductively isolated from each other, the three species of hydromyine rodents have a 100% level of amino acid sequence identity at the putative sperm-combining site. This finding does not support the view that this site is under positive selective pressure. The sequence data obtained in this study may have important conservation implications for the dissemination of immunocontraception directed against M. musculus using ZPC antibodies.     

Checklist of helminth parasites of the cane toad Bufo marinus (Anura: Bufonidae) from Mexico

Thirty-four adult cane toads Bufo marinus L. (12 males and 22 females) collected from 2 localities in Mexico (Cerro de Oro and Temascal Dams, Oaxaca) in September 2003 were examined for helminth parasites. In total, 14,749 helminths belonging to 14 taxa were collected. Included were 2 adult digeneans (Choledocystus hepaticus, Mesocoelium monas); 1 larval cestode (an unidentified pseudophyllidean); and 11 nematodes, including 3 species of larvae (Contracaecum sp., Physaloptera sp., Physocephalus sexalatus) and 8 species of adults (Aplectana itzocanensis, Cosmocerca sp., Cruzia morleyi, Ochoterenella digiticauda, Oswaldocruzia sp., Raillietnema sp., Rhabdias americanus, and Rhabdiasfuelleborni). Higher species richness was recorded in B. marinus from Cerro de Oro (12 taxa versus 9 in those from Temascal); hosts from both localities shared 7 taxa. There were 25 new locality records, and 2 taxa were registered in Mexico for the first time. To date, 112 helminth species have been recorded parasitizing B. marinus along its native and introduced range of distribution, with 40.5% of them reported from Mexico.     

Geographic variation in rodent-flea relationships in the presence of black-tailed prairie dog colonies

We characterized the relationship between fleas and their rodent hosts in the presence of prairie dog colonies and compared them to adjacent assemblages away from colonies. We evaluated the rodent-flea relationship by quantifying prevalence, probability of infestation, flea load, and intensity of fleas on rodents. As prairie dog burrows provide refugia for fleas, we hypothesized that prevalence, flea load, and intensity would be higher for rodents that are associated with black-tailed prairie dog colonies. Rodents were trapped at off- and on-colony grids, resulting in the collection of 4,509 fleas from 1,430 rodents in six study areas. The rodent community composition varied between these study areas. Flea species richness was not different between prairie dog colonies and the surrounding grasslands (p = 0.883) but was positively correlated with rodent species richness (p = 0.055). Prairie dog colonies did not increase the prevalence of fleas (p > 0.10). Flea loads on rodents did not vary between off- and on-colony grids at three of the study areas (p > 0.10). Based on the prevalence, infestation rates, and flea loads, we identified Peromyscus maniculatus, Onychomys leucogaster, and two Neotoma species as important rodent hosts for fleas and Aetheca wagneri, Orchopeus leucopus, Peromyscopsylla hesperomys, Pleochaetis exilis, and Thrassisfotus as the most important fleas associated with these rodents. Prairie dog colonies did not seem to facilitate transmission of fleas between rodent hosts, and the few rodent-flea associations exhibited significant differences between off- and on-colony grids.