Risk Of Parasite Transmission Research Articles

Cradle or plague pit? Illuminated cages increase the transmission risk of parasites from copepods to coregonids

Cestode-infested copepods (Cyclops abyssorum) are strongly attracted to illuminated cages used for rearing juvenile whitefish (Coregonus sp.) in Lake Fuschlsee, Austria. In the submersed cages, artificial light at night concentrated zooplanktonic organisms about 40-fold compared to normal abundances outside cages, thus ensuring a sufficient food supply for planktivorous fish. However, inside the cage the average prevalence of Triaenophorus spp. and Proteocephalus spp. within C. abyssorum was 5.4 and 5.1 times higher than in the pelagic zone of the lake. In absolute numbers 3.83Ind.L−1 within the cage hosted a procercoid compared to 0.04Ind.L−1 in the open water. After three months in the cage, 90% of the coregonids harboured on average 5 plerocercoids of Triaenophorus crassus and 100% were parasitized by Proteocephalus exiguus. Total length and weight of whitefish with T. crassus plerocercoids were lower than of those without the parasite. Rearing fish for stocking purposes in illuminated cages increases the risk of cestode accumulation in fish populations. We discourage from using this method in lakes with cestode-problems or suggest to at least release fish before procercoids of Triaenophorus spp. occur in the zooplankton to prevent massive infestations inside the cage.

Parasite Transmission Risk From Geophagic and Foraging Behavior in Chacma Baboons

Numerous behavioral and ecological factors are associated with parasite transmission. One factor explored in human research, but absent from nonhuman primate research, is parasite transmission from soil ingestion. Human studies suggest geophagy, the regular and deliberate consumption of soil, increases risk of soil-transmitted helminth (STH) infection. Geophagy, which is prevalent in nonhuman primates, has several positive associations: gastrointestinal distress alleviation, possible mineral supplementation, and bacterial infection prevention. Our objective was to determine whether STH transmission was possible from deliberate or accidental soil ingestion, in a troop of chacma baboons (Papio hamadryas ursinus) that engaged in geophagy, foraged on the terrestrial substrata, and had a Trichuris sp. sample prevalence of 100%. We collected and analyzed 80 soil samples from geophagy and ground foraging sites on and around Wildcliff Nature Reserve, South Africa. Forty soil samples were collected from sites where soil was consumed, and 40 were collected from sites where soil was not consumed. At geophagy sites, the number of Trichuris sp. eggs recovered varied significantly between areas used and unused by the baboons, suggesting behavior is an important factor. In contrast, at foraging sites, there was only a tendency to recover more eggs at used than unused areas, and we propose egg recovery was influenced by fecal contamination that occurred throughout foraging stands. The difference in egg recovery between used areas at geophagy sites and used areas at foraging sites was not significant. These preliminary findings suggest both geophagy and foraging sites are a potential source of STH infection for this troop. Whether geophagy benefits outweigh the potential cost of parasite reinfection for this baboon troop is unknown, so we encourage future research on the influence that host foraging behavior may have on parasite reinfection.

Tritrichomonas foetus isolates from cats and cattle show minor genetic differences in unrelated loci ITS-2 and EF-1α

The protozoan parasite Tritrichomonas foetus is well known as an important causative agent of infertility and abortion in cattle (bovine trichomonosis). This World Organisation for Animal Health (O.I.E.) notifiable disease is thought to be under control in many countries including Switzerland. In recent studies, however, T. foetus has also been identified as an intestinal parasite that causes chronic large-bowel diarrhoea in cats. Since the feline isolates were considered indistinguishable from bovine isolates, the possibility and risk of parasite transmission from cats to cattle and vice versa has been intensively discussed in current literature. Therefore, we investigated if cat and cattle isolates are genetically distinct from each other or in fact represent identical genotypes. For this purpose, two independent genetic loci were selected that turned out to be well-suited for a PCR sequencing-based genotyping of trichomonad isolates: (i) previously published internal transcribed spacer region 2 (ITS-2) and (ii) a semi-conserved sequence stretch of the elongation factor-1 alpha (EF-1α) gene used for the first time in the present study. Respective comparative analyses revealed that both loci were sufficiently variable to allow unambiguous genetic discrimination between different trichomonad species. Comparison of both genetic loci confirmed that T. suis and T. mobilensis are phylogenetically very close to T. foetus. Moreover, these two genetic markers were suited to define host-specific genotypes of T. foetus. Both loci showed single base differences between cat and cattle isolates but showed full sequence identity within strains from either cat or cattle isolates. Furthermore, an additional PCR with a forward primer designed to specifically amplify the bovine sequence of EF-1α was able to discriminate bovine isolates of T. foetus from feline isolates and also from other trichomonads. The implications these minor genetic differences may have on the biological properties of the distinct isolates remain to be investigated.

Sex-Specific Differences in Shoaling Affect Parasite Transmission in Guppies

BackgroundIndividuals have to trade-off the costs and benefits of group membership during shoaling behaviour. Shoaling can increase the risk of parasite transmission, but this cost has rarely been quantified experimentally. Guppies (Poecilia reticulata) are a model system for behavioural studies, and they are commonly infected by gyrodactylid parasites, notorious fish pathogens that are directly transmitted between guppy hosts.Methodology/Principal FindingsParasite transmission in single sex shoals of male and female guppies were observed using an experimental infection of Gyrodactylus turnbulli. Parasite transmission was affected by sex-specific differences in host behaviour, and significantly more parasites were transmitted when fish had more frequent and more prolonged contact with each other. Females shoaled significantly more than males and had a four times higher risk to contract an infection.Conclusions/SignificanceIntersexual differences in host behaviours such as shoaling are driven by differences in natural and sexual selection experienced by both sexes. Here we show that the potential benefits of an increased shoaling tendency are traded off against increased risks of contracting an infectious parasite in a group-living species.

Risk of parasite transmission influences perceived vulnerability to disease and perceived danger of disease-relevant animals

Adaptationist view proposes that emotions were shaped by natural selection and their primary function is to protect humans against predators and/or disease threat. This study examined cross-cultural and inter-personal differences in behavioural immune system measured by disgust, fear and perceived danger in participants from high (Turkey) and low (Slovakia) pathogen prevalence areas. We found that behavioural immune system in Turkish participants was activated more than those of Slovakian participants when exposed to photographs depicting disease-relevant cues, but not when exposed to disease-irrelevant cues. However, participants from Slovakia, where human to human disease transmission is expected to be more prevalent than in Turkey, showed lower aversion in Germ Aversion subscale supporting hypersensitiveness of the behavioural immune system. Having animals at home was less frequent both in Turkey and in participants who perceived higher danger about disease relevant animals. Participants more vulnerable to diseases reported higher incidence of illness last year and considered perceived disease-relevant animals more dangerous than others. Females showed greater fear, disgust and danger about disease-relevant animals than males. Our results further support the finding that cultural and inter-personal differences in human personality are influenced by parasite threat.

Long-term survey on Trichinella prevalence in wildlife of Slovakia

In Slovakia, monitoring the prevalence of Trichinella spp. in wildlife was performed since 2000 in the main reservoir animals, the red fox (Vulpes vulpes) and wild boar (Sus scrofa), using artificial digestion method as recommended by International Commission on Trichinellosis. The results of investigation performed in 5270 red foxes showed that Trichinella infection is widespread across Slovakia and prevalence increased significantly from 4.9% in 2000 to 20.5% in 2007. Recently, a higher Trichinella prevalence (0.11%) in wild boars was also demonstrated. The results indicate that foxes and wild boars are involved in the spread of Trichinella, although the latter host species seems to play a secondary role in the maintenance of the sylvatic cycle in Slovakia. Trichinella britovi is the predominant species circulating in Slovakia, both in foxes and wild boars, and Trichinella spiralis occurs only sporadically. Mixed infections of T. britovi and Trichinella pseudospiralis were recorded in 2005 in one wild boar from Eastern Slovakia and in 2006 in one red fox from the same region. These findings are important with respect to an outbreak caused by T. pseudospiralis in a pig farm in the same district 3 years ago. This study provides a complex picture on Trichinella occurrence in all regions of Slovakia and may be a good basis for evaluating the risk of parasite transmission to the domestic cycle and human beings.

Novel Peptide Marker Corresponding to Salivary Protein gSG6 Potentially Identifies Exposure to Anopheles Bites

BackgroundIn order to improve malaria control, and under the aegis of WHO recommendations, many efforts are being devoted to developing new tools for identifying geographic areas with high risk of parasite transmission. Evaluation of the human antibody response to arthropod salivary proteins could be an epidemiological indicator of exposure to vector bites, and therefore to risk of pathogen transmission. In the case of malaria, which is transmitted only by anopheline mosquitoes, maximal specificity could be achieved through identification of immunogenic proteins specific to the Anopheles genus. The objective of the present study was to determine whether the IgG response to the Anopheles gambiae gSG6 protein, from its recombinant form to derived synthetic peptides, could be an immunological marker of exposure specific to Anopheles gambiae bites.Methodology/Principal FindingsSpecific IgG antibodies to recombinant gSG6 protein were observed in children living in a Senegalese area exposed to malaria. With the objective of optimizing Anopheles specificity and reproducibility, we designed five gSG6-based peptide sequences using a bioinformatic approach, taking into consideration i) their potential antigenic properties and ii) the absence of cross-reactivity with protein sequences of other arthropods/organisms. The specific anti-peptide IgG antibody response was evaluated in exposed children. The five gSG6 peptides showed differing antigenic properties, with gSG6-P1 and gSG6-P2 exhibiting the highest antigenicity. However, a significant increase in the specific IgG response during the rainy season and a positive association between the IgG level and the level of exposure to Anopheles gambiae bites was significant only for gSG6-P1.Conclusions/SignificanceThis step-by-step approach suggests that gSG6-P1 could be an optimal candidate marker for evaluating exposure to Anopheles gambiae bites. This marker could be employed as a geographic indicator, like remote sensing techniques, for mapping the risk of malaria. It could also represent a direct criterion of efficacy in evaluation of vector control strategies.

Intestinal Parasites of Free-ranging, Semicaptive,and Captive Pongo abelii in Sumatra, Indonesia

We collected fecal samples from 32 free-ranging, 19 semicaptive, and 54 captive Sumatran orangutans on Sumatra from 1998 until 2004 and screened them for gastrointestinal parasites. Our objectives were to compare the intestinal parasites of free-ranging, semicaptive, and captive orangutans and to evaluate the risk of parasite transmission in orangutan reintroduction programs. We identified 4 genera of Protozoa, 7 genera of nematodes, 1 trematode sp., and 1 cestode sp. The prevalence of Balantidium coli in free-ranging orangutans was significantly higher than in captive individuals. However, the prevalence of Strongyloides sp. was higher in captive than in free-ranging orangutans. Free-ranging female orangutans had a significantly higher total prevalence of intestinal parasites than that of males. We found no significant difference between parasite prevalences in different age groups. Compared to gorillas and chimpanzees, orangutans carry a smaller variety of protozoan and nematode species. Strongyloides sp. infections form the highest risk in reintroduction programs as crowding, ground-dwelling, and poor hygiene in captive and semicaptive orangutans may cause a constant reinfection.

Toxoplasma gondii infection in sheep from Haute-Vienne, France: Seroprevalence and isolate genotyping by microsatellite analysis

Ingesting meat of free-range livestock, mainly sheep, is associated with human toxoplasmosis in European countries. Data on Toxoplasma gondii infection in French ovine livestock are relatively scarce. Sera from 164 lambs and 93 ewes slaughtered in Haute-Vienne district, France, were tested by a direct agglutination test. Antibodies to T. gondii were found in 36 (22.0%) lambs and in 61 (65.6%) ewes. In addition, to attempt parasite isolation for genotyping, hearts from 50 other ewes were obtained from a local slaughterhouse, and were screened by a direct agglutination test. T. gondii was isolated in 8 of 30 seropositive hearts bioassayed in mice. All isolates were type II by genetic characterization at five microsatellite loci ( TUB2, TgM-A, W35, B17, B18). These results indicate that ovines slaughtered in France may be highly infected by T. gondii with a potential risk of parasite transmission to humans by consumption of undercooked meat. Multilocus microsatellite analysis shows the predominance of type II in sheep as previously described in humans.

Focos de dirofilariose canina na Ilha do Marajó: um fator de risco para a saúde humana

The occurrence of human pulmonary dirofilariasis maintains a relation with the prevalence of Dirofilaria immitis infection in the canine population. Several mosquito species are vectors of this nematode. Canine blood samples collected in Pingo d'Agua and União villages, Salvaterra municipality (Marajó Island, Pará), in June, 2004 (n = 34) and April, 2005 (N = 90) were analyzed. Parasitological and immunological (ELISA--kit SNAP(R) 3DX Biobrasil) diagnoses were compared following the examination of 34 samples. The prevalence in the population (N = 90) was evaluated by means of ELISA. ELISA revealed more positive samples (25/34; 73.5%) than thick smears (23/34, 67.6%) or Knott (21/34, 61.8%), but the differences were not significant (p > 0.05). The frequency of D. immitis infection was 58% in dogs ranging from 0-2 years old, whereas in older dogs it was 100%. The prevalence of canine dirofilariasis was high in Pingo d'Agua and Vila União (53.5%), indicating the risk of parasite transmission to the people in this area.

COMMENTARIES ON Evolutionary Foundations of Cultural Variation: Evoked Culture and Mate Preferences

Let's talk first about parasites. Given the persistent influence that bacteria, viruses, and other parasites have had on human evolution (Van Blerkom, 2003), it's astonishing that so little scientific attention has been devoted to their impact on human psychology and hu man culture. There are extensive bodies of research documenting the role of parasites on evolved patterns of animal cognition and behavior. Many studies reveal that mammals are sensitive to signs of parasitic infec tion in potential mates and avoid mating with individu als who show those signs (e.g., Kavaliers, Colwell, Braun, & Choleris, 2003). These kinds of effects are not restricted to mating contexts either. Bullfrog tad poles selectively prefer to swim near healthy tadpoles, while avoiding tadpoles that carry parasitic infections (Kiesecker, Skelly, Beard, & Preisser, 1999). Closer to home (phylogenetically speaking), chimpanzees react with unusual violence toward other chimpanzees that show the physical symptoms of debilitating diseases (Goodall, 1986). It is likely that the human mind too is characterized by mechanisms designed to recognize and respond negatively to individuals who show signs of parasite infections-and to do so especially under conditions in which the risk of parasitic infection is es pecially high (Kurzban & Leary, 2001; Schaller, Park, & Faulkner, 2003). In recent years, empirical studies have docu mented the presence of just such mechanisms and their consequences on social cognition and behavior. Some of these consequences are straightforward: We stigmatize and avoid sick people, especially when we perceive their sickness to be contagious (Crandall & Moriarty, 1995). Additional consequences are more subtle. We not only stigmatize people who really are sick; we also stigmatize people who may be perfectly healthy but who-on the basis of some superficial feature-appear to pose a risk of parasite transmis sion. And we do so especially under conditions in which we feel especially vulnerable to parasitic infec tion. Xenophobic reactions to foreigners are stronger among folks who feel personally vulnerable to germs and disease (Faulkner, Schaller, Park, & Duncan, 2004). Individuals with deviant or nonprototypical morphological features-people who are disfigured or disabled, or who are grossly obese-are similarly stigmatized, and, again, this stigmatization seems to occur especially strongly among people who are per sonally concerned about their own vulnerability to disease (Park, 2005; Park, Faulkner, & Schaller, 2003). The preference for physically attractive mates might also be understood within this context. Physi cal unattractiveness is based substantially on per ceived deviations from a population prototype (Langlois & Roggman, 1990). Consequently, the sub jective assessment of unattractiveness may serve as a cue indicating the potential presence of a parasitic in fection at the moment, as well as a cue indicating po tential susceptibility to parasitic infections in the fu ture. Within this conceptual context, it is no surprise that people care about the physical attractiveness of someone with whom they are destined to spend a lot of time with and that they care especially within pop ulations that have historically been more vulnerable to debilitating parasitic infections (Gangestad & Buss, 1993). Now, in the results reported by Gangestad, Haselton, and Buss (this issue), we en counter even more impressive evidence that para site-prevalence influences mate-selection preferences, and this influence occurs across an even broader set of preferences.

Infectivity of promastigotes and amastigotes of Leishmaniainfantum in a canine model for leishmaniosis

Seven dogs experimentally infected with amastigotes or culture promastigotes of Leishmania infantum MON-1 were observed for a period of up to 38 months. The course of infection was monitored by clinical and parasitological examinations, haematological and serum protein analysis, and by anti-leishmania antibody levels. Two of the three amastigote-inoculated dogs developed a symptomatic infection with haematological and protein alterations, and a strong humoral immune response. The third dog was asymptomatic with no haematological or protein alterations and developed a steady humoral response. Four promastigote-inoculated dogs remained asymptomatic throughout the observation period, with only transient antibody responses to leishmanial antigen, and no haematological or protein alterations. The detection of the parasite in biological material obtained at necropsy showed that dogs with no clinical signs or other manifestations of disease may be infected. This indicates that asymptomatic carriers may be present in the canine population, but not identifiable by the usual serological tests, and suggests that epidemiological surveys based on serology may underestimate the prevalence of canine leishmaniosis and the parasite transmission risk.