Comparison of different genetic distances to test isolation by distance between populations.

Studying isolation by distance can provide useful demographic information. To analyze isolation by distance from molecular data, one can use some kind of genetic distance or coalescent simulations. Molecular markers can often display technical caveats, such as PCR-based amplification failures (null alleles, allelic dropouts). These problems can alter population parameter inferences that can be extracted from molecular data. In this simulation study, we analyze the behavior of different genetic distances in Island (null hypothesis) and stepping stone models displaying varying neighborhood sizes. Impact of null alleles of increasing frequency is also studied. In stepping stone models without null alleles, the best statistic to detect isolation by distance in most situations is the chord distance DCSE. Nevertheless, for markers with genetic diversities HS<0.4-0.5, all statistics tend to display the same statistical power. Marginal sub-populations behave as smaller neighborhoods. Metapopulations composed of small sub-population numbers thus display smaller neighborhood sizes. When null alleles are introduced, the power of detection of isolation by distance is significantly reduced and DCSE remains the most powerful genetic distance. We also show that the proportion of null allelic states interact with the slope of the regression of FST/(1-FST) as a function of geographic distance. This can have important consequences on inferences that can be made from such data. Nevertheless, Chapuis and Estoup's FreeNA correction for null alleles provides very good results in most situations. We finally use our conclusions for reanalyzing and reinterpreting some published data sets.

Co-infection of Toxoplasma gondii with HBV in HIV-infected and uninfected pregnant women in Burkina Faso.

Toxoplasma gondii infections can induce serious complications in HIV-infected pregnant women, leading to miscarriage; favour the mother-to-child transmission of HBV and HIV and birth defects. The purposes of this study were: (1) to quantify IgM and IgG antibodies to Toxoplasma gondii in HIV-seropositive and seronegative pregnant women, (2) to identify hepatitis B antigens (HBsAg) in pregnant women and (3) to determine T. gondii and HBV co-infections among these patients. The study was conducted at Centre Medical Saint Camille, in Burkina Faso from January to June 2009. A total of 276 HIV-infected and uninfected pregnant women were included. All women had less than 32 weeks of amenorrhoea and were aged from 19 to 42 years. Toxoplasma gondii antibodies and HBsAg were detected using ELISA method. In addition, women freely agreed to answer a questionnaire. The results of our investigations revealed that, among these pregnant women, 38.8% were illiterates, 50.4% were housewives and only 5.4% were civil servants. Positive T. gondii-specific IgM (4.7%) and IgG (27.2%) were detected. In this study, we found that HIV-seropositive status seem to be associated with great prevalence rates of both T. gondii (31.9 vs. 22.5%) and HBV (13.0 vs. 5.8%). The elevated co-infection rate in HIV-positive women suggested that they are exposed to T. gondii and HBV infections prevalently because of their immune depression. Therefore, to reduce the prevalence of T. gondii and HBV among HIV-seropositive pregnant women, lamivudine could be included in their HEART and women should follow healthy lifestyle formation.

Portals of entry and systemic localization of proliferative gill disease organisms in channel catfish Ictalurus punctatus.

Immunized rabbit serum adsorbed in live catfish was used in indirect fluorescent antibody test (IFAT) to detect developmental life stages of Henneguya ictaluri n. sp. This myxozoan parasite is associated with proliferative gill disease in channel catfish Ictalurus punctatus (Rafinesque) in the USA. Specific pathogen free fingerlings were experimentally infected with the actinosporean stage of H. ictaluri and necropsied 24, 48, 72, and 96 h post-infection. At 24 h post-infection parasite stages were observed primarily in the gastric mucosa and submucosa but were also observed in the skin and buccal cavity. Ovoid organisms were detected in heart and blood vessels of the liver. From 48 to 72 h after exposure, fewer fluorescent organisms were located in all organs, with the exception of the gills, than were observed at 24 h. These organisms appeared to be degenerating except for those in the gills, which appeared to be multinucleated. By 96 h post-infection, the organisms could not be detected in fish tissues with the exception of the stages in the gills, which appeared to be a preferred site of development. Throughout the entire 96 h period of study, no stage of the organism was detected in the brain. Infected tissue sections treated with non-immune rabbit serum and non-infected tissue sections treated with immune rabbit sera all showed negative results by IFAT.

Seasonal pattern of inhibition of Ostertagia ostertagi in calves in northeast Mississippi.

The composition of, and seasonal changes in, populations of gastrointestinal parasites of calves in northeast Mississippi were determined for 10 months post-weaning. After weaning on 15 October, 20 mixed breed beef steers were grazed together on a 4 ha fescue/bermudagrass pasture. From November through August of the following year, two of the calves were removed each month for necropsy and counting of gastrointestinal nematodes. Eight species of worms were found: Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, Bunostomum phlebotomum, Cooperia spp., Trichostrongylus colubriformis, Oesophagostomum spp., and Trichuris ovis. During all months, Ostertagia ostertagi and Cooperia spp. combined comprised at least 89% of gastrointestinal nematode burdens. Cooperia spp. represented 92.6% of the total worm burden of calves in November but declined to about 56% in January and February. From March through August, Ostertagia ostertagi comprised at least 79% of the worms from calves. Numbers of inhibited Ostertagia ostertagi increased markedly from February to March and remained at high levels prior to resumption of development in August. The proportion of Trichostrongylus axei remained about 4% throughout the year, but the highest numbers were recorded in the summer months. Other species were minor components of the worm population. These data indicate that with respect to Ostertagia ostertagi, northeast Mississippi can be considered a summer inhibition zone.

Evidence for arrested development of abomasal nematodes in white-tailed deer.

White-tailed deer (Odocoileus virginianus) obtained from Noxubee National Wildlife Refuge, Noxubee County, Mississippi (USA) during April (n = 3), June (n = 5), September (n = 5), and November (n = 5) 1989, were necropsied for counting and identification of adult and larval stages of abomasal nematodes. Fourth-stage larvae (L4) (n < or = 25) from each deer were randomly selected for measurement of total worm length and width. Adults of four worm species were found: Mazamastrongylus odocoilei, M. pursglovei, Ostertagia mossi, and O. dikmansi. There were no differences between months in adult male worm burdens for all species except O. dikmansi for which the April worm burden was greatest (P < or = 0.05). Overall, the length of L4 ranged from 929 to 4,361 microns. There were no significant differences (P > 0.05) between months in the mean length (1,334 to 1,532 microns) of L4. Except for low numbers of developing fourth-stage larvae (length > 1,650 microns) in April (2.6%), June (7.4%), September (11.3%), and November (3.7%), worms were early fourth-stage larvae (EL4) or fully developed adults. Overall, the proportion of EL4 in individual deer ranged from 19 to 97%; in male (n = 3) and female (n = 15) deer the proportions of EL4 were 22.5% and 67%, respectively. The mean proportions of EL4 in female deer were 51.4% (April), 63.2% (June), 78.1% (September), and 74.7% (November), but there was no difference (P > 0.05) among the 4 months.(ABSTRACT TRUNCATED AT 250 WORDS)

[Incidence of trypanosomiasis on wildlife of a game ranch in Burkina Faso]. / Incidence de la trypanosomose sur la faune sauvage d'un ranch de gibier au Burkina Faso.

Blood samples from 203 wild animals kept on a game ranch in Burkina Faso were examined by the "buffy coat" technique following microhaematocrite centrifugation in capillary tubes. Anaemia was assessed according to the value of packed cell volume (PCV). A thin smear and thick blood film from each animal were prepared and examined for detection of Babesia, Anaplasma, Theileria, Microfilaria. The infection rate and parasitaemia were assessed in each animal species. For each animal species examined, sex, age, weight, ectoparasites and trypanosoma species (Duttonella, Nannomonas, Trypanozoon, Megatrypanum groups) were recorded. The average of trypanosomosis rate was 15.3%, with considerable variations in relation to the behaviour and biotope showed a specific receptivity to the different trypanosome species. Receptivity was higher in Tragelaphus scriptus et Hippotragus equinus than in other species. Trypanosomosis infection did not seem to affect the health status of the monitored wild animals. This study confirms that wild animals are a reservoir of trypanosomes. The role they play in the epizootiology of animal trypanosomosis varies according to animal species, glossina and trypanosome involved and depends on the interactions between these three parameters in a given situation.