Individual Parasite Load Research Articles

Season, Body Condition, and Sex Variation of Ectoparasite Abundance in Tarentola delalandii (Squamata: Phyllodactylidae) from Two Ecologically Contrasting Populations of Tenerife (Canary Islands)

Individual parasite load depends on several factors such as sex, body size or climatic conditions. In turn, parasites may produce several short- and long-term pathologies. Herein, we analyze the ectoparasite load of the Geckobia mite in two ecologically contrasting populations (north and south of Tenerife) of the gecko Tarentola delalandii. For this purpose, we performed random transects to capture geckos under rocks in each population and counted all mites found on any part of each gecko's body. A generalized linear model showed no significant effect on mite abundance of site, season, sex (within population), condition index, or temperature of the refuges. However, there were significant effects of the interactions between season by condition index and season by sex (nested within population). Parasitism was higher in individuals with lower body index values in autumn–winter than those with higher body condition in spring–summer. Moreover, females of the northern population were more heavily parasitized than males and juveniles in the year's cooler months. We discuss several potential explanations for these results.

Host-Parasite Relationship-Nematode Communities in Populations of Small Mammals.

Simple SummaryIntestinal nematodes were analyzed in three small rodent species: Apodemus sylvaticus, Apodemus flavicollis, and Myodes glareolus. In total, 15 species of nematodes were identified. We studied the relationship between the parasitological parameters (individual parasite species richness IndPSR and individual parasite load IndPL) and morphological characteristics (body mass, body condition index BCI, and spleen mass). In all of the studied species, our results showed that animals in a better condition (BCI) had significantly higher parasite species richness, as we had expected. Furthermore, we showed that females of the same BCI as males were parasitized with more parasite species in A. flavicollis. Contrary to our expectations, the spleen mass did not reflect changes in the level of parasitism, but in M. glareolus, a smaller spleen was related to a higher parasite load. Since the spleen is just part of the complex immune response, it is possible that the presence of nematode parasite species provokes, in small rodent species, a response at the other levels of the immune system.Nematode burdens and variation in morphological characteristics were assessed in eighty-eight animals from three host species (Apodemus sylvaticus, Apodemus flavicollis, and Myodes glareolus) from eight localities in Serbia. In total, 15 species of nematodes were identified, and the overall mean parasite species richness (IndPSR) was 1.61 per animal (1.98 in A. flavicollis, 1.43 in M. glareolus, and 0.83 in A. sylvaticus). Furthermore, the studied host species significantly differed in individual parasite load (IndPL) and in the following morphological characters: spleen mass, body condition index (BCI), and body mass. We aimed to analyze the relationship between the burden of intestinal nematodes, on one hand, and the body conditions of the host and its capability to develop immune defends on the other. Spleen mass was considered as a measure of immune response. In all host species, larger animals with a better condition (higher BCI) were infected with more parasites species (IndPSR), while parasite load was not related to BCI. Only in A. flavicollis were males significantly larger, but females of the same sizes were infected with more parasite species. This female-biased parasitism is contrary to the theoretical expectation that males should be more parasitized, being larger, more active, with a wider home range. Although the spleen size was significantly correlated with body condition and body mass, IndPSR was not related to spleen mass in any studied species, but in M. galareolus, we found that a smaller spleen was related to higher infection intensity (IndPL).

Gastro-intestinal parasitism and control practices in dairy cattle in North-west Cameroon (Central Africa).

The main objective of this study was to assess the gastrointestinal parasitism in relation with the worm control practices (WCP) in dairy cattle in areas of major importance for dairy/milk production of Cameroon. Fresh fecal samples were randomly collected from 402 cattle from August to October 2016 in North West Cameroon, and analyze using the McMaster technique. Data on WCP were collected using a questionnaire. A total of 11 parasites species were identified: Trichostrongylus sp. (5.97%); Oesophagostomum sp. (5.47%); Haemonchus sp. (2.48%); Bonostomum sp. (1.74); Cooperia sp. (1.49%). Toxocara sp (0.24%); Ostertagia sp. (0.50%); Nematodirus sp. (0.74%); Trichuris sp. (0.50%); Moniezia sp. (0.50%); Eimeria sp. (0.50%). The mean individual parasite load for helminthes and protozoa ranged from 100 to 400 eggs per gram of feces (epg) and 333-400 oocysts per gram of feces (opg), respectively. Most farmers (95.12%) used conventional drugs (Albendazole, Doramectin, Fenbendazole, Ivermectin.) to deworm animals as compared with traditional phytotherapy (e.g., Carica papaya leaves) (4.88%). The mean epg/opg in animals treated with conventional drugs was significantly higher (p < 0.05) than in those receiving traditional treatment. Animals treated less than four times a year with conventional drugs had the highest (p < 0.05) mean epg/opg compared with animals treated four to six times a year. This study suggests that treating at least four times a year with conventional drugs, and at least two times a year with traditional approaches could help reducing GIP burden in dairy cattle in North West Cameroon. Since the majority of farmers use conventional drugs, it is imperative for them to appropriately use these conventional drugs for a better control of GIP on their farms.

Prevalence of Intestinal Parasites amongst selected age groups within Okada, South –South Nigeria.

This study was conducted to determine the prevalence of intestinal parasites from volunteered individuals in the study site. A total of 300 stool samples, comprising 150 females and 150 males were collected randomly from the study population in Ovia North-East Local Government Area in Edo State, aged between 1 and 60 years. The stool samples were aseptically collected and examined using both direct smear method and formol ether sedimentation techniques to determine the individual parasite load of the sampled population. The age group of 16-20 had the highest number of participants 102(34%) while the age group of 6-10, 51-55 and 56-60 had the least number of participants of 3(1%) respectively. Out of the 300 stool samples examined 87, (29%) were positive with intestinal parasites while 213(71%) were negative, not having any intestinal parasitic infection However the age group of 11-15(N=10) and 31-35(N=10) had the highest prevalence rate of 11.5%, while the lowest prevalence (1%) was found in individuals of ages 41-60 years. There was no intestinal parasites found among the individuals below11 years of age.. Of the 150 male candidates examined, 57 (65.5%) were infected with intestinal parasites. On the other hand, their female counterparts had a total prevalence of 34.5%. A total number of six parasitic species were isolated from the fecal specimens. These were Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercolaris, Entamoeba coli, Hookworms and Entamoeba histolytica. Ascaris lumbricoides had the highest prevalence rate (12%), while Trichuris trichiura and Strongyloides stercolaris had the least prevalence rate (1%) respectively. The intestinal parasite infection and age were negatively correlated and there was a significant difference between the male and female infection rates (p&lt;0.05).

Interactions between Environmental Contaminants and Gastrointestinal Parasites: Novel Insights from an Integrative Approach in a Marine Predator.

Environmental contaminants and parasites are ubiquitous stressors that can affect animal physiology and derive from similar dietary sources (co-exposure). To unravel their interactions in wildlife, it is thus essential to quantify their concurring drivers. Here, the relationship between blood contaminant residues (11 trace elements and 17 perfluoroalkyl substances) and nonlethally quantified gastrointestinal parasite loads was tested while accounting for intrinsic (sex, age, and mass) and extrinsic factors (trophic ecology inferred from stable isotope analyses and biologging) in European shags Phalacrocorax aristotelis. Shags had high mercury (range 0.65–3.21 μg g–1 wet weight, ww) and extremely high perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) residues (3.46–53 and 4.48–44 ng g–1 ww, respectively). Males had higher concentrations of arsenic, mercury, PFOA, and PFNA than females, while the opposite was true for selenium, perfluorododecanoic acid (PFDoA), and perfluooctane sulfonic acid (PFOS). Individual parasite loads (Contracaecum rudolphii) were higher in males than in females. Females targeted pelagic-feeding prey, while males relied on both pelagic- and benthic-feeding organisms. Parasite loads were not related to trophic ecology in either sex, suggesting no substantial dietary co-exposure with contaminants. In females, parasite loads increased strongly with decreasing selenium:mercury molar ratios. Females may be more susceptible to the interactive effects of contaminants and parasites on physiology, with potential fitness consequences.

Effect of Host Condition on Intestinal Parasite Load and Prevalence in Malapterurus Electricus (Gmelin, 1789) ( Siluriformes: Malapteruridae ) in Lekki Lagoon, Lagos, Nigeria

Host condition had effect on therate of infection and greater effect on intestinal parasite load in Malapterurus electricus . These vary among sex, sizes and weights of conspecific individuals. This was investigated over a period of two years.A total of 340 fishes from the lagoon were caught and dissected for intestinal helminth parasites and the condition factors of all individuals were determined. Median condition (K 2.33) was used in grouping the individuals. The rate of infection was higher among individuals of high condition status (29.41% to 31.76%). Male individuals of high condition had greater infection rate than their low condition males (33.65% to 29.25%), but their female individuals had a lower infection rate compared to the low condition females (28.88% to 29.41%). Percentage parasite load among conspecific males of high and low condition within the weight 10g to 60g had their parasite load as 28.76% and 15.93% respectively. The females of low condition had a greater parasite load of 13.27% compared with the high condition females, 7.08%. Within the low and high condition individuals of weight 10g to 60g and 60g to 130g, the males had higher load than their females. Low condition males of length, 9cm to 15cm and 15cm to 22cm had greater parasite load than their high condition males, 9 – 15cm (14.61%, 10.62%) and 15 – 22cm (22.57%, 11.06%) respectively. This also applies to the females, 15 – 22cm (8.41%, 3.54%) except the females within length of 9cm to 15cm (10.62, 11.06%). Pre-existing variations in the competitive ability of hosts has potentially important implication for parasite infections as well as their individual parasite load. Monitoring health condition of fish population provides vital information for ecotoxicologist and toxicologist for improved environmental monitoring. Keywords : Intestinal Parasite, Prevalence, Malapterurus, Electricus , Lekki Lagos.

Host nutrition alters the variance in parasite transmission potential.

The environmental conditions experienced by hosts are known to affect their mean parasite transmission potential. How different conditions may affect the variance of transmission potential has received less attention, but is an important question for disease management, especially if specific ecological contexts are more likely to foster a few extremely infectious hosts. Using the obligate-killing bacterium Pasteuria ramosa and its crustacean host Daphnia magna, we analysed how host nutrition affected the variance of individual parasite loads, and, therefore, transmission potential. Under low food, individual parasite loads showed similar mean and variance, following a Poisson distribution. By contrast, among well-nourished hosts, parasite loads were right-skewed and overdispersed, following a negative binomial distribution. Abundant food may, therefore, yield individuals causing potentially more transmission than the population average. Measuring both the mean and variance of individual parasite loads in controlled experimental infections may offer a useful way of revealing risk factors for potential highly infectious hosts.

Can mixed-species groups reduce individual parasite load? A field test with two closely related poeciliid fishes (Poecilia reticulata and Poecilia picta).

Predation and parasitism are two of the most important sources of mortality in nature. By forming groups, individuals can gain protection against predators but may increase their risk of being infected with contagious parasites. Animals might resolve this conflict by forming mixed-species groups thereby reducing the costs associated with parasites through a relative decrease in available hosts. We tested this hypothesis in a system with two closely related poeciliid fishes (Poecilia reticulata and Poecilia picta) and their host-specific monogenean ectoparasites (Gyrodactylus spp.) in Trinidad. Fish from three different rivers were sampled from single and mixed-species groups, measured and scanned for Gyrodactylus. The presence and abundance of Gyrodactylus were lower when fish of both species were part of mixed-species groups relative to single-species groups. This is consistent with the hypothesis that mixed-species groups provide a level of protection against contagious parasites. We discuss the importance of potentially confounding factors such as salinity and individual fish size.

Factors influencing the magnitude of strongyle egg-shedding in horses

simultaneously at frequent intervals is still common in Finland, even though horse practitioners are now promoting the use of targeted selective treatment. In order to evaluate selective therapy as an option to reduce anthelmintic use we conducted a study on ten stables. Objectives: 1. To estimate parasite loads of individual horses 2. To analyse risk factors for high egg counts 3. To observe the effects of different anthelmintics to the individual parasite loads. One to eight fecal samples per horse were collected from 215 (86 geldings, 100 mares, 24 stallions) horses (mean age 9.1 yrs, min 0 and max 29) from ten stables in Finland during a one-year study period. The samples were analysed by modified McMaster-technique by the Finnish Food Safety Authority (Evira). Antiparasitic treatment history of each horse was collected by a questionnaire. Majority of the adult horses maintained low epg-values ( 20 years). Majority of the adult horses are able to maintain low epgvalues and therefore frequent treatments with anthelmintics to all horses should be discouraged. Horses should be sampled and treated based on individual risk factors and epg-values. Further analysis of the data will bring more information on how the risk of high epg-count is affected by grazing, season and treatment intervals.

Parasite Transmission in Social Interacting Hosts: Monogenean Epidemics in Guppies

BackgroundInfection incidence increases with the average number of contacts between susceptible and infected individuals. Contact rates are normally assumed to increase linearly with host density. However, social species seek out each other at low density and saturate their contact rates at high densities. Although predicting epidemic behaviour requires knowing how contact rates scale with host density, few empirical studies have investigated the effect of host density. Also, most theory assumes each host has an equal probability of transmitting parasites, even though individual parasite load and infection duration can vary. To our knowledge, the relative importance of characteristics of the primary infected host vs. the susceptible population has never been tested experimentally.Methodology/Principal FindingsHere, we examine epidemics using a common ectoparasite, Gyrodactylus turnbulli infecting its guppy host (Poecilia reticulata). Hosts were maintained at different densities (3, 6, 12 and 24 fish in 40 L aquaria), and we monitored gyrodactylids both at a population and individual host level. Although parasite population size increased with host density, the probability of an epidemic did not. Epidemics were more likely when the primary infected fish had a high mean intensity and duration of infection. Epidemics only occurred if the primary infected host experienced more than 23 worm days. Female guppies contracted infections sooner than males, probably because females have a higher propensity for shoaling.Conclusions/SignificanceThese findings suggest that in social hosts like guppies, the frequency of social contact largely governs disease epidemics independent of host density.

Variety matters: adaptive genetic diversity and parasite load in two mouse opossums from the Brazilian Atlantic forest

The adaptive potential of a species to a changing environment and in disease defence is primarily based on genetic variation. Immune genes, such as genes of the major histocompatibility complex (MHC), may thereby be of particular importance. In marsupials, however, there is very little knowledge about natural levels and functional importance of MHC polymorphism, despite their key role in the mammalian evolution. In a previous study, we discovered remarkable differences in the MHC class II diversity between two species of mouse opossums (Gracilinanus microtarsus, Marmosops incanus) from the Brazilian Atlantic forest, which is one of the most endangered hotspots for biodiversity conservation. Since the main forces in generating MHC diversity are assumed to be pathogens, we investigated in this study gastrointestinal parasite burden and functional associations between the individual MHC constitution and parasite load. We tested two contrasting scenarios, which might explain differences in MHC diversity between species. We predicted that a species with low MHC diversity would either be under relaxed selection pressure by low parasite diversity (‘Evolutionary equilibrium’ scenario), or there was a recent loss in MHC diversity leading to a lack of resistance alleles and increased parasite burden (‘Unbalanced situation’ scenario). In both species it became apparent that the MHC class II is functionally important in defence against gastrointestinal helminths, which was shown here for the first time in marsupials. On the population level, parasite diversity did not markedly differ between the two host species. However, we did observe considerable differences in the individual parasite load (parasite prevalence and infection intensity): while M. incanus revealed low MHC DAB diversity and high parasite load, G. microtarsus showed a tenfold higher population wide MHC DAB diversity and lower parasite burden. These results support the second scenario of an unbalanced situation.

Major histocompatibility complex variation and age-specific endoparasite load in subadult European rabbits

Genes of the major histocompatibility complex (MHC) play a fundamental role in the vertebrate immune response and are amongst the most polymorphic genes in vertebrate genomes. It is generally agreed that the highly polymorphic nature of the MHC is maintained through host-parasite co-evolution. Two nonexclusive mechanisms of selection are supposed to act on MHC genes: superiority of MHC heterozygous individuals (overdominance) and an advantage for rare MHC alleles. However, the precise mechanisms and their relative importance are still unknown. Here, we examined MHC dependent parasite load in European rabbits (Oryctolagus cuniculus) from a distinct population with low MHC diversity (three alleles, six genotypes). Using a multivariate approach, we tested for associations of individual MHC class II DRB constitution and the rabbits' intestinal burden with nematodes and coccidia. Rabbits having a particular allele showed lower infestations with hepatic coccidia (E.stiedai). However, a comparison of all six genotypes in the population revealed that carriers of this allele only benefit when they are heterozygous, and furthermore, MHC heterozygosity in general did not affect individual parasite load. In conclusion, this study suggests an immunogenetic basis of European rabbit resistance to hepatic coccidiosis, which can strongly limit survival to maturity in this species. Our study gives a complex picture of MHC-parasite correlations, unveiling the limits of the classical hypotheses of how MHC polymorphism is maintained in natural systems.

Refuge sharing network predicts ectoparasite load in a lizard

Living in social groups facilitates cross-infection by parasites. However, empirical studies on indirect transmission within wildlife populations are scarce. We investigated whether asynchronous overnight refuge sharing among neighboring sleepy lizards, Tiliqua rugosa, facilitates indirect transmission of its ectoparasitic tick, Amblyomma limbatum. We fitted 18 neighboring lizards with GPS recorders, observed their overnight refuge use each night over 3 months, and counted their ticks every fortnight. We constructed a transmission network to estimate the cross-infection risk based on asynchronous refuge sharing frequencies among all lizards and the life history traits of the tick. Although self-infection was possible, the network provided a powerful predictor of measured tick loads. Highly connected lizards that frequently used their neighbors’ refuges were characterized by higher tick loads. Thus, indirect contact had a major influence on transmission pathways and parasite loads. Furthermore, lizards that used many different refuges had lower cross- and self-infection risks and lower tick loads than individuals that used relatively fewer refuges. Increasing the number of refuges used by a lizard may be an important defense mechanism against ectoparasite transmission in this species. Our study provides important empirical data to further understand how indirectly transmitted parasites move through host populations and influence individual parasite loads.

Within colony dynamics ofNosema bombiinfections: disease establishment, epidemiology and potential vertical transmission

Successful growth and transmission is a prerequisite for a parasite to maintain itself in its host population. Nosema bombi is a ubiquitous and damaging parasite of bumble bees, but little is known about its transmission and epidemiology within bumble bee colonies. The impact of host demography and colony life-cycle on the transmission and reproduction of N. bombi were examined in Bombus lucorum colonies. Parasite success was highest when infecting colonies where larval exposure to the parasite was high. The later individual bees were born in the colony life-cycle, the higher their infection intensity, but after eclosion individual parasite loads did not increase, indicating either host control of the parasite, a balance between internal infection and the production of transmission stages, or a switch in the parasite's growth strategy after eclosion to the production of transmission stages. Finally, trans-ovarial vertical transmission of N. bombi was suggested using molecular probes.

Preferential Growth of Taenia crassiceps Cysticerci in Female Mice Holds Across Several Laboratory Mice Strains and Parasite Lines

A retrospective study of our 14-yr records on experimental Taenia crassiceps (ORF(fast) line) cysticercosis (n = 1,198) shows that in 16 of 17 different mice strains, female mice are more frequently infected and carry larger individual parasite loads than males. However, sexual differences in parasite loads significantly varies between strains in relation to their different genetic backgrounds (BALB > C57Bl = OTHERS > C3H). The coefficient of variation in all female mice is significantly smaller than that of all males, an indication of males' more potent, but erratically effective, restraint of cysticercus growth. Similar positive growth bias for female mice is shown by other lines of cysticerci, i.e., HYG(slow) and WFU(slow). These results contravene the usual expectation of female hosts being more resistant than males to parasite infections, and they point to the multiple factors that combined determine sex related differences of mice to experimental cysticercosis infection.

Variation in intensity of a parasitic mite (Spinturnix myoti) in relation to the reproductive cycle and immunocompetence of its bat host (Myotis myotis)

Given the intimate association in host–parasite systems, parasites are expected to initiate their own reproduction when vulnerable hosts become abundant and/or when adult hosts are less resistant. In this study, we examined the variation in the intensities of a blood‐sucking mite (Spinturnix myoti, Acarina) with respect to the reproductive cycle and immunocompetence of its host, the greater mouse‐eared bat Myotis myotis. Reproductive, pregnant females were less immunocompetent and harboured more parasites than nonreproductive females, whilst, during lactation, immunocompetence was positively associated with female body mass. There was a dramatic increase in the T‐cell response of gravid females with the advancement of gestation, which coincided with a diminution of individual parasite loads and a progressive switch of parasites from adults to juveniles. The latter not only harboured greater numbers of mites than adult female bats, but they also exhibited gravid parasites in higher proportions, indicating that juvenile hosts are more attractive for parasite reproduction than adult females.

Immunization of pigs against Taenia solium cysticercosis: factors related to effective protection

Fifty-six (56) pigs were immunized against Taenia solium cysticercosis with antigens from Taenia crassiceps metacestodes, in a variety of protocols, and then challenged orally with Taenia solium proglottids or eggs. Results of immunization (expressed as individual parasite loads) ranged from significant reduction of parasite loads (host protection) to clear increase (parasite facilitation) in apparent relation to the immunogen dose, adjuvant employed and genetic background of the pigs. In all trials, however, immunized pigs harboured more damaged cysticerci than controls, indicating that immunization does induce some restrictions to parasite survival even if these are eventually overwhelmed by other parasite-promoting factors. Western blots in immunized-protected pigs indicated antigens of 242, 234, 118, 77, 55 and 45 kDa as possibly being involved in immunological protection.

Nasal botflies of migrating wildebeest from western Zambia

Summary A migratory population of wildebeest (Connochaetes taurinus) in Liuwa Plain National Park in the Western Province of Zambia was sampled for nasal bots (Diptera: Oestridae: Oestrinae) during 1975–78. Infestations from 32 antelope included Gedoelstia spp. (two species), Oestrus aureoargentatus and O. variolosus. A total of 1913 second and third instar larvae was recorded from the sinuses and nasal septa with individual parasite loads varying from 4 to 144 bots. No obvious pathogenicity was attributable to these oestrids, all four species of which were judged to be multivoltine in this habitat. The significance of this voltinism in relation to the migratory course of the wildebeest is discussed together with a consideration of parasite densities and the potential threat of myiasis to domestic livestock in the area.