Variant -and individual dependent nature of persistent Anaplasma phagocytophilum infection

Background

Anaplasma phagocytophilum is the causative agent of tick-borne fever in ruminants and human granulocytotropic anaplasmosis (HGA). The bacterium is able to survive for several months in immune-competent sheep by modifying important cellular and humoral defence mechanisms. Little is known about how different strains of A. phagocytophilum propagate in their natural hosts during persistent infection.

Methods

Two groups of five lambs were infected with each of two 16S rRNA gene variants of A. phagocytophilum, i.e. 16S variant 1 which is identical to GenBank no M73220 and 16S variant 2 which is identical to GenBank no AF336220, respectively. The lambs were infected intravenously and followed by blood sampling for six months. A. phagocytophilum infection in the peripheral blood was detected by absolute quantitative real-time PCR.

Results

Both 16S rRNA gene variants of A. phagocytophilum established persistent infection for at least six months and showed cyclic bacteraemias, but variant 1 introduced more frequent periods of bacteraemia and higher number of organisms than 16S rRNA gene variant 2 in the peripheral blood.

Conclusion

Organisms were available from blood more or less constantly during the persistent infection and there were individual differences in cyclic activity of A. phagocytophilum in the infected animals. Two 16S rRNA gene variants of A. phagocytophilum show differences in cyclic activity during persistent infection in lambs.     

Ecological Factors Characterizing the Prevalence of Bacterial Tick-Borne Pathogens in Ixodes ricinus Ticks in Pastures and Woodlands

Ecological changes are recognized as an important driver behind the emergence of infectious diseases. The prevalence of infection in ticks depends upon ecological factors that are rarely taken into account simultaneously. Our objective was to investigate the influences of forest fragmentation, vegetation, adult tick hosts, and habitat on the infection prevalence of three tick-borne bacteria, Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, and Rickettsia sp. of the spotted fever group, in questing Ixodes ricinus ticks, taking into account tick characteristics. Samples of questing nymphs and adults were taken from 61 pastures and neighboring woodlands in central France. The ticks were tested by PCR of pools of nymphs and individual adults. The individual infection prevalence was modeled using multivariate regression. The highest infection prevalences were found in adult females collected in woodland sites for B. burgdorferi sensu lato and A. phagocytophilum (16.1% and 10.7%, respectively) and in pasture sites for Rickettsia sp. (8.7%). The infection prevalence in nymphs was lower than 6%. B. burgdorferi sensu lato was more prevalent in woodlands than in pastures. Forest fragmentation favored B. burgdorferi sensu lato and A. phagocytophilum prevalence in woodlands, and in pastures, the B. burgdorferi sensu lato prevalence was favored by shrubby vegetation. Both results are probably because large amounts of edges or shrubs increase the abundance of small vertebrates as reservoir hosts. The Rickettsia sp. prevalence was maximal on pasture with medium forest fragmentation. Female ticks were more infected by B. burgdorferi sensu lato than males and nymphs in woodland sites, which suggests an interaction between the ticks and the bacteria. This study confirms the complexity of the tick-borne pathogen ecology. The findings support the importance of small vertebrates as reservoir hosts and make a case for further studies in Europe on the link between the composition of the reservoir host community and the infection prevalence in ticks.Ecological modifications are recognized as one of the main forces behind the emergence of infectious diseases (37). As vectors and wildlife are very sensitive to environmental conditions, ecological changes are expected to have a particular impact on the epidemiology of vector-borne diseases and those with a wildlife origin (29, 48). Several studies have highlighted the influence of factors such as climate change and habitat fragmentation on the risk of tick-borne diseases (20, 67). The risk of a tick-borne disease being transmitted to humans or to animals is closely linked to the prevalence of pathogens in ticks questing for hosts (38, 58). In turn, infection prevalence directly depends on the probability of ticks feeding on an infected reservoir host. This probability results from a combination of the intrinsic characteristics of the species involved (e.g., the host species feeding preference of the tick and the ability of the pathogen to infect different host species) and the characteristics of the host community (e.g., the likelihood of contact between ticks and infected reservoir hosts) that vary in time and space. Due to the difficulty of directly assessing the host community, it may be characterized indirectly by studying landscape and habitat features (3, 9). The increased fragmentation of deciduous forests, for example, favors infection prevalence in ticks that are the agents of Lyme disease in the eastern United States because this fragmentation pattern favors the abundance of a highly competent host reservoir, the white-footed mouse (Peromyscus leucopus) (1, 12). However, studies of the effect of habitat fragmentation on different tick-borne pathogens are scarce (25, 40, 67). Most only report on the infection prevalence of pathogens in ticks according to sampling locations, the stage of tick development, and their sex (18, 56); few studies take into account the interplay or simultaneous effects of explanatory environmental factors (2).In Europe, the Ixodes ricinus tick is one of the most important vectors for animal and human pathogens, especially bacteria (21). These include pathogenic species of the complex Borrelia burgdorferi sensu lato, the agent of Lyme borreliosis, the most prevalent vector-borne human disease in Europe (57); Anaplasma phagocytophilum, the agent of human and animal granulocytic anaplasmosis, considered to be an emerging disease both in human and in animals (8, 61); and Rickettsia helvetica of the spotted fever group, known to be responsible for nonspecific fevers in humans (28).Although they share the same tick vector, B. burgdorferi sensu lato, A. phagocytophilum, and R. helvetica have different ecological cycles and transmission patterns which influence the infection prevalence at different stages of a tick''s life. For B. burgdorferi sensu lato, the maintenance cycle of the bacteria depends on immature stages of I. ricinus ticks feeding on infected reservoir hosts, mainly small rodents and birds that feed on the ground (36, 62). For A. phagocytophilum, small mammals and ruminants are reservoir hosts (16, 22, 69). In contrast to the other two pathogens, R. helvetica is transovarially and sexually transmitted in ticks (13, 33). Ticks are thus considered to be a reservoir host for the bacteria. Small rodents are also suspected to be reservoir hosts in Europe (45), while the role of ungulates remains unknown (60).It is increasingly recognized that a better understanding of the variation of the prevalence of pathogens in ticks within regions of endemicity is critical to the rational design and monitoring of control programs (47). Our objective was to run an exploratory analysis to test the influence of a range of factors on variations in the prevalence of B. burgdorferi sensu lato, A. phagocytophilum, and Rickettsia sp. of the spotted fever group in questing I. ricinus ticks. The factors considered were two habitats (pasture and woodland), forest fragmentation metrics, the vegetation around and near the pasture, and adult tick hosts (deer and cattle); and the analysis took into account factors linked to tick characteristics (tick sex, tick stage, and the density of questing nymphs). Consequently, we analyzed ticks collected in the field for the presence of DNA from the three bacteria and ran an exploratory statistical model using multivariate regression.     

Prevalence of <Emphasis Type="Italic">Borrelia burgdorferi</Emphasis> sensu lato and <Emphasis Type="Italic">Anaplasma phagocytophilum</Emphasis> in questing <Emphasis Type="Italic">Ixodes ricinus</Emphasis> ticks in relation to the density of wild cervids

Background

Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum have been considered as pathogens in animals and humans. The role of wild cervids in the epidemiology is not clear. We analyzed questing Ixodes ricinus ticks collected in spring for these pathogens from sites with high (Fjelløyvær and Strøm) and low density (Tjore, Hinnebu and Jomfruland) of wild cervids to study the spread of the pathogens in questing ticks.

Methods

For detection of Anaplasma phagocytophilum a 77-bp fragment in the msp 2 gene was used. Detection of Borrelia burgdorferi sensu lato was performed using the FL6 and FL7 primers according to sequences of conserved regions of the fla gene. The Osp A gene located on the linear 49-kb plasmid was used as target in multiplex PCR for genotyping. Genospecies-specific primers were used in the PCR for Borrelia burgdorferi sensu stricto, B. afzelii and B. garinii.

Results

Infection rates with Borrelia spp. were significantly lower at Fjelløyvær and Strøm compared to Tjore and Hinnebu; Fjelløyvær vs. Tjore (χ² = 20.27, p < 0.0001); Fjelløyvær vs. Hinnebu (χ² = 24.04, p < 0.0001); Strøm vs. Tjore (χ² = 11.47, p = 0.0007) and Strøm vs. Hinnebu (χ² = 16.63, p < 0.0001). The Borrelia genospecies were dominated by. B. afzelii (82%) followed by B. garinii (9.7%) and B. burgdorferi sensu stricto (6.9%). B. burgdorferi s.s. was only found on the island of Jomfruland. The infection rate of Anaplasma phagocytophilum showed the following figures; Fjelløyvær vs Hinnebu (χ² = 16.27, p = 0.0001); Strøm vs. Tjore (χ² = 13.16, p = 0.0003); Strøm vs. Hinnebu (χ² = 34.71, p < 0.0001); Fjelløyvær vs. Tjore (χ² = 3.19, p = 0.0742) and Fjelløyvær vs. Støm (χ² = 5.06, p = 0.0245). Wild cervids may serve as a reservoir for A. phagocytophilum. Jomfruland, with no wild cervids but high levels of migrating birds and rodents, harboured both B. burgdorferi s.l. and A. phagocytophilum in questing I. ricinus ticks. Birds and rodents may play an important role in maintaining the pathogens on Jomfruland.

Conclusion

The high abundance of roe deer and red deer on the Norwegian islands of Fjelløyvær and Strøm may reduce the infection rate of Borrelia burgdorferi sensu lato in host seeking Ixodes ricinus, in contrast to mainland sites at Hinnebu and Tjore with moderate abundance of wild cervids. The infection rate of Anaplasma phagocytophilum showed the opposite result with a high prevalence in questing ticks in localities with a high density of wild cervids compared to localities with lower density.

     

Reduced Weight Gain Due to Subclinical Anaplasma phagocytophilum (Formerly Ehrlichia phagocytophila) Infection

Tick-borne fever (TBF) is caused by the rickettsia Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila) and is a common disease in sheep in areas of Norway infested by Ixodes ricinus ticks. TBF can cause both direct and indirect losses to sheep kept on tick-infested pastures. In the present work we studied a sheep flock of 26 ewes and 50 lambs on pasture from May until September. No cases of TBF had earlier been observed on this pasture. Blood samples from lambs with a reduced weekly weight gain were collected and analysed for A. phagocytophilum infection by blood smear examination. In addition, at the end of the study, sera from all lambs were analysed by an indirect fluorescent antibody assay (IFA) to determine the antibody titre to E. equi. No clinical signs of tick-borne infections were observed, except in one lamb. However, 30 (60%) of the lambs grazing on this pasture became infected with A. phagocytophilum, and the infected lambs had a reduced weight gain (mean) of 3.8 kg compared with the uninfected lambs. The present study indicates that A. phagocytophilum infection may be widespread and contribute to considerable productivity losses even on pastures with no apparent tick infestation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic diversity of Actinobacillus lignieresii isolates from different hosts

Background

Bovine babesiosis is regarded as a limited health problem for Norwegian cows, and the incidence has decreased markedly since the 1930s. Rare cases of babesiosis in splenectomised humans from infection with Babesia divergens and B.venatorum have been described. The objective of this study was to determine whether birds can introduce Babesia-infected ticks. There are between 30 and 85 million passerine birds that migrate to Norway every spring.

Methods

Passerine birds were examined for ticks at four bird observatories along the southern Norwegian coast during the spring migrations of 2003, 2004 and 2005. The presence of Babesia was detected in the nymphs of Ixodes ricinus by real-time PCR. Positive samples were confirmed using PCR, cloning and phylogenetic analyses.

Results

Of 512 ticks examined, real-time PCR revealed five to be positive (1.0%). Of these, four generated products that indicated the presence of Babesia spp.; each of these were confirmed to be from Babesia venatorum (EU1). Two of the four B. venatorum-positive ticks were caught from birds having an eastern migratory route (P< 0.001).

Conclusions

Birds transport millions of ticks across the North Sea, the Skagerrak and the Kattegat every year. Thus, even with the low prevalence of Babesia-infected ticks, a substantial number of infected ticks will be transported into Norway each year. Therefore, there is a continuous risk for introduction of new Babesia spp. into areas where I. ricinus can survive.     

VirB10 vaccination for protection against <Emphasis Type="Italic">Anaplasma phagocytophilum</Emphasis>

Background

Human granulocytic anaplasmosis (HGA) is a tick-borne disease caused by the etiologic agent Anaplasma phagocytophilum. HGA was designated a nationally notifiable disease in the United States in 1998. Currently there are no vaccines available against HGA. Conserved membrane proteins that are subdominant in Anaplasma species, such as VirB9 and VirB10, may represent better vaccine targets than the variable immunodominant surface proteins. VirB9 and VirB10 are constituents of the Type 4 secretion system (T4SS) that is conserved amongst many intracellular bacteria and performs essential functions for invasion and survival in host cells.

Results

Immunogenicity and contribution to protection, provided after intramuscular vaccination of plasmid DNA encoding VirB9-1, VirB9-2, and VirB10 followed by inoculation of homologous recombinant proteins, in a prime-boost immunization strategy was evaluated in a murine model of HGA. Recombinant VirB9-1-, VirB9-2-, and VirB10-vaccinated mice developed antibody responses that specifically reacted with A. phagocytophilum organisms. However, only the mice vaccinated with VirB10 developed a significant increase in IFN-γ CD4⁺ T cells and partial protection against challenge with A. phagocytophilum.

Conclusions

This work provides evidence that A. phagocytophilum T4SS VirB10 is partially protective in a murine model against infection in an IFN-γ-dependent fashion and suggests that this protein may be a potential vaccine candidate against this and possibly other pathogenic bacteria with a T4SS.

     

First molecular detection of <Emphasis Type="Italic">Anaplasma phagocytophilum</Emphasis> in the hard tick <Emphasis Type="Italic">Rhipicephalus haemaphysaloides</Emphasis> in Taiwan

Anaplasma phagocytophilum is transmitted mainly by hard ticks and can cause potentially fatal granulocytic anaplasmosis in humans, but its occurrence in ticks in Taiwan has never been investigated although this pathogen has been detected in Taiwanese rodents before. Ticks collected from small mammals in Hualien, eastern Taiwan, were assayed for Anaplasma infections; infections of Rickettsia and Apicomplexa protozoans were also studied. Of the 270 individually assayed Rhipicephalus haemaphysaloides ticks, A. phagocytophilum was identified in a nymphal tick. Parasites most similar to Anaplasma bovis, Rickettsia rickettsii, Rickettsia sp. TwKM01, and at least seven apicomplexan species (including genera Cryptosporidium, Hepatozoon, and Theileria) were also identified. This study shows that A. phagocytophilum does occur in the hard tick in Taiwan, although whether R. haemaphysaloides can vector this pathogen remains to be determined. This work also reveals a high diversity of tick-borne bacteria and protozoans circulating in a small region and calls for further research on their potential risks for human health.     

Seroprevalence of <Emphasis Type="Italic">Borrelia burgdorferi</Emphasis> sensu lato and <Emphasis Type="Italic">Anaplasma phagocytophilum</Emphasis> in Danish horses

Background

Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum are able to infect horses. However, the extend to which Danish horses are infected and seroconvert due to these two bacteria is unknown. The aim of the present study was to evaluate the seroprevalence of B. burgdorferi sensu lato and A. phagocytophilum in Danish horses.

Methods

A total of 390 blood samples collected from all major regions of Denmark and with a geographical distribution corresponding to the density of the Danish horse population were analyzed. All samples were examined for the presence of antibodies against B. burgdorferi sensu lato and A. phagocytophilum by the use of the SNAP^®4DX ^® ELISA test.

Results

Overall, 29.0% of the horses were seropositive for B. burgdorferi sensu lato whereas 22.3% were seropositive for A. phagocytophilum.

Conclusions

Antibodies against B burgdorferi sensu lato and A. phagocytophilum are commonly found among Danish horses thus showing that Danish horses are frequently infected by these organisms.

     

Low-molecular-weight heparin reduces hyperoxia-augmented ventilator-induced lung injury via serine/threonine kinase-protein kinase B

Introduction

Factors explaining the greater susceptibility of preterm infants to severe lower respiratory infections with respiratory syncytial virus (RSV) remain poorly understood. Fetal/newborn lambs are increasingly appreciated as a model to study key elements of RSV infection in newborn infants due to similarities in lung alveolar development, immune response, and susceptibility to RSV. Previously, our laboratory demonstrated that preterm lambs had elevated viral antigen and developed more severe lesions compared to full-term lambs at seven days post-infection. Here, we compared the pathogenesis and immunological response to RSV infection in lungs of preterm and full-term lambs.

Methods

Lambs were delivered preterm by Caesarian section or full-term by natural birth, then inoculated with bovine RSV (bRSV) via the intratracheal route. Seven days post-infection, lungs were collected for evaluation of cytokine production, histopathology and cellular infiltration.

Results

Compared to full-term lambs, lungs of preterm lambs had a heightened pro-inflammatory response after infection, with significantly increased MCP-1, MIP-1α, IFN-γ, TNF-α and PD-L1 mRNA. RSV infection in the preterm lung was characterized by increased epithelial thickening and periodic acid-Schiff staining, indicative of glycogen retention. Nitric oxide levels were decreased in lungs of infected preterm lambs compared to full-term lambs, indicating alternative macrophage activation. Although infection induced significant neutrophil recruitment into the lungs of preterm lambs, neutrophils produced less myeloperoxidase than those of full-term lambs, suggesting decreased functional activation.

Conclusions

Taken together, our data suggest that increased RSV load and inadequate immune response may contribute to the enhanced disease severity observed in the lungs of preterm lambs.     

Two initial vaccinations with the Bm86-based Gavacplus vaccine against Rhipicephalus (Boophilus) microplus induce similar reproductive suppression to three initial vaccinations under production conditions

Background

The cattle tick, Rhipicephalus (Boophilus) microplus, affects livestock production in many regions of the world. Up to now, the widespread use of chemical acaricides has led to the selection of acaricide-resistant ticks and to environmental contamination. Gavac^plus is a subunit vaccine based on the recombinant Bm86 tick antigen expressed in yeast, capable to control infestations of R. microplus under controlled and production conditions. The vaccine constitutes the core element of broad control programs against this ectoparasite, in which acquired immunity in cattle to Bm86 is combined with a rational use of acaricides. At present, the conventional vaccine scheme consists of three doses that should be administered at weeks 0, 4 and 7, followed by a booster every six months.

Results

In this study we assayed a reduction in the number of the initial doses of Gavac^plus, evaluated the time course and the level of bovine anti-Bm86 antibodies elicited, and analyzed the vaccine effect on ticks engorging on immunized cattle under production conditions. Following three different immunization schemes, the bovines developed a strong and specific immune response characterized by elevated anti-Bm86 IgG titers. A reduction in the weight of engorging female ticks, in the weight of the eggs laid and also in R. microplus viable eggs percentage was obtained by using only two doses of Gavac^plus administered at weeks 0 and 4, followed by a booster six months later. This reduction did not differ from the results obtained on ticks engorging on cattle immunized at weeks 0, 4 and 7. It was also demonstrated that anti-Bm86 antibody titers over 1:640, measured in bovines immunized at weeks 0 and 4, were sufficient to affect weight and reproductive potential of female ticks as compared with ticks engorging on unvaccinated animals. In addition, no statistically significant differences were detected in the average weight of eggs laid by ticks engorged on immunized cattle that showed anti-Bm86 specific titers in the range of 1:640 to 1:81920.

Conclusion

The administration of two initial doses of Gavac^plus containing 100 μg of Bm86 antigen to non-immunized cattle under production conditions is sufficient to affect the weight and the reproductive capacity of R. microplus engorging females. According to these results, cattle herds' manipulation and vaccine costs could be potentially reduced with a positive impact on the implementation of integrated control programs against R. microplus.     

Antipyretic effect of ibuprofen in Gabonese children with uncomplicated falciparum malaria: a randomized, double-blind, placebo-controlled trial

Background

The protection afforded by human erythrocyte polymorphisms against the malaria parasite, Plasmodium falciparum, has been proposed to be due to reduced ability of the parasite to invade or develop in erythrocytes. If this were the case, variable levels of parasitaemia and rates of seroconversion to infected-erythrocyte variant surface antigens (VSA) should be seen in different host genotypes.

Methods

To test this hypothesis, P. falciparum parasitaemia and anti-VSA antibody levels were measured in a cohort of 555 asymptomatic children from an area of intense malaria transmission in Papua New Guinea. Linear mixed models were used to investigate the effect of α⁺-thalassaemia, complement receptor-1 and south-east Asian ovalocytosis, as well as glucose-6-phosphate dehydrogenase deficiency and ABO blood group on parasitaemia and age-specific seroconversion to VSA.

Results

No host polymorphism showed a significant association with both parasite prevalence/density and age-specific seroconversion to VSA.

Conclusion

Host erythrocyte polymorphisms commonly found in Papua New Guinea do not effect exposure to blood stage P. falciparum infection. This contrasts with data for sickle cell trait and highlights that the above-mentioned polymorphisms may confer protection against malaria via distinct mechanisms.     

Sleeping site ecology,but not sex,affect ecto- and hemoparasite risk,in sympatric,arboreal primates (<Emphasis Type="Italic">Avahi occidentalis</Emphasis> and <Emphasis Type="Italic">Lepilemur edwardsi</Emphasis>)

Background

A central question in evolutionary parasitology is to what extent ecology impacts patterns of parasitism in wild host populations. In this study, we aim to disentangle factors influencing the risk of parasite exposure by exploring the impact of sleeping site ecology on infection with ectoparasites and vector-borne hemoparasites in two sympatric primates endemic to Madagascar. Both species live in the same dry deciduous forest of northwestern Madagascar and cope with the same climatic constraints, they are arboreal, nocturnal, cat-sized and pair-living but differ prominently in sleeping site ecology. The Western woolly lemur (Avahi occidentalis) sleeps on open branches and frequently changes sleeping sites, whereas the Milne-Edward’s sportive lemur (Lepilemur edwardsi) uses tree holes, displaying strong sleeping site fidelity. Sleeping in tree holes should confer protection from mosquito-borne hemoparasites, but should enhance the risk for ectoparasite infestation with mites and nest-adapted ticks. Sex may affect parasite risk in both species comparably, with males bearing a higher risk than females due to an immunosuppressive effect of higher testosterone levels in males or to sex-specific behavior. To explore these hypotheses, ectoparasites and blood samples were collected from 22 individuals of A. occidentalis and 26 individuals of L. edwardsi during the dry and rainy season.

Results

L. edwardsi, but not A. occidentalis, harbored ectoparasites, namely ticks (Haemaphysalis lemuris [Ixodidae], Ornithodoros sp. [Argasidae]) and mites (Aetholaelaps trilyssa, [Laelapidae]), suggesting that sleeping in tree holes promotes infestation with ectoparasites. Interestingly, ectoparasites were found solely in the hot, rainy season with a prevalence of 75% (N = 16 animals). Blood smears were screened for the presence and infection intensity of hemoparasites. Microfilariae were detected in both species. Morphological characteristics suggested that each lemur species harbored two different filarial species. Prevalence of microfilarial infection was significantly lower in L. edwardsi than in A. occidentalis. No significant difference in infection intensity between the two host species, and no effect of season, daytime of sampling or sex on prevalence or infection intensity was found. In neither host species, parasite infection showed an influence on body weight as an indicator for body condition.

Conclusions

Our findings support that sleeping site ecology affects ectoparasite infestation in nocturnal, arboreal mammalian hosts in the tropics, whereas there is no significant effect of host sex. The influence of sleeping site ecology to vector-borne hemoparasite risk is less pronounced. The observed parasite infections did not affect body condition and thus may be of minor importance for shaping reproductive fitness. Findings provide first evidence for the specific relevance of sleeping site ecology on parasitism in arboreal and social mammals. Further, our results increase the sparse knowledge on ecological drivers of primate host-parasite interactions and transmission pathways in natural tropical environments.

     

The role of anti-malarial drugs in eliminating malaria

Background

Pregnant women develop protective anti-VSA IgG1 and IgG3 when infected by Plasmodium falciparum. The major target of IgG from serum of infected pregnant women is VAR2CSA.

Methods

In this study, ELISA was used to compare the level of VAR2CSA DBL5ε- specific IgG subclasses at enrolment and at delivery in a cohort of pregnant women in Senegal. All antibody measures were analysed in relation to placental infection according to parity.

Results

The results show an interaction between immune response to placental malaria and parity. A higher level of anti- DBL5ε- IgG3 at enrolment and a higher increase between enrolment and delivery were found in primigravidae who presented with uninfected placenta at delivery in comparison to those who presented with an infection of the placenta. However, high antibody level at delivery was associated with the infection of the placenta in multigravidae.

Conclusion

This high level of IgG3 in uninfected primigravidae suggests a protective role of these antibodies in this susceptible group, highlighting the importance of VAR2CSA in general and of some of its variants still to be defined, in the induction of protective immunity to pregnancy malaria.     

Increased mortality associated with HTLV-II infection in blood donors: a prospective cohort study

Background

The Sykes' monkey and related forms (Cercopithecus mitis) make up an abundant, widespread and morphologically diverse species complex in eastern Africa that naturally harbors a distinct simian immunodeficiency virus (SIVsyk). We carried out a retrospective serological survey of SIV infection from both wild and captive Sykes' monkeys from Kenya. We compared two commercially available, cross-reactive ELISA tests using HIV antigens with a novel SIVsyk antigen-specific Western blot assay and analyzed the data by origin, subspecies, age and sex.

Results

The SIVsyk antigen-specific Western blot assay detected more serum samples as positive than either of the cross-reactive ELISA assays. Using this assay, we found that seroprevalence is higher than previously reported, but extremely variable in wild populations (from 0.0 to 90.9%). Females were infected more often than males in both wild and captive populations. Seropositive infants were common. However, no seropositive juveniles were identified.

Conclusion

We have developed a specific and sensitive Western blot assay for anti-SIVsyk antibody detection. Sykes' monkeys are commonly infected with SIVsyk, but with extremely variable prevalence in the wild. Higher infection prevalence in females suggests predominantly sexual transmission. High infection prevalence in infants, but none in juveniles, suggests maternal antibodies, but little or no vertical transmission.     

Comparative genomics of first available bovine Anaplasma phagocytophilum genome obtained with targeted sequence capture

Background

Anaplasma phagocytophilum is a zoonotic and obligate intracellular bacterium transmitted by ticks. In domestic ruminants, it is the causative agent of tick-borne fever, which causes significant economic losses in Europe. As A. phagocytophilum is difficult to isolate and cultivate, only nine genome sequences have been published to date, none of which originate from a bovine strain.Our goals were to; 1/ develop a sequencing methodology which efficiently circumvents the difficulties associated with A. phagocytophilum isolation and culture; 2/ describe the first genome of a bovine strain; and 3/ compare it with available genomes, in order to both explore key genomic features at the species level, and to identify candidate genes that could be specific to bovine strains.

Results

DNA was extracted from a bovine blood sample infected by A. phagocytophilum. Following a whole genome capture approach, A. phagocytophilum DNA was enriched 197-fold in the sample and then sequenced using Illumina technology. In total, 58.9% of obtained reads corresponded to the A. phagocytophilum genome, covering 85.3% of the HZ genome. Then by performing comparisons with nine previously-sequenced A. phagocytophilum genomes, we determined the core genome of these ten strains. Following analysis, 1281 coding DNA sequences, including 1001 complete sequences, were detected in the A. phagocytophilum bovine genome, of which four appeared to be unique to the bovine isolate. These four coding DNA sequences coded for "hypothetical proteins of unknown function” and require further analysis. We also identified nine proteins common to both European domestic ruminants tested.

Conclusion

Using a whole genome capture approach, we have sequenced the first A. phagocytophilum genome isolated from a cow. To the best of our knowledge, this is the first time that this method has been used to selectively enrich pathogenic bacterial DNA from samples also containing host DNA. The four proteins unique to the A. phagocytophilum bovine genome could be involved in host tropism, therefore their functions need to be explored.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-973) contains supplementary material, which is available to authorized users.     

Impact of two myostatin (MSTN) mutations on weight gain and lamb carcass classification in Norwegian White Sheep (Ovis aries)

Background

Our aim was to estimate the effect of two myostatin (MSTN) mutations in Norwegian White Sheep, one of which is close to fixation in the Texel breed.

Methods

The impact of two known MSTN mutations was examined in a field experiment with Norwegian White Sheep. The joint effect of the two MSTN mutations on live weight gain and weaning weight was studied on 644 lambs. Carcass weight gain from birth to slaughter, carcass weight, carcass conformation and carcass fat classes were calculated in a subset of 508 lambs. All analyses were carried out with a univariate linear animal model.

Results

The most significant impact of both mutations was on conformation and fat classes. The largest difference between the genotype groups was between the wild type for both mutations and the homozygotes for the c.960delG mutation. Compared to the wild types, these mutants obtained a conformation score 5.1 classes higher and a fat score 3.0 classes lower, both on a 15-point scale.

Conclusions

Both mutations reduced fatness and increased muscle mass, although the effect of the frameshift mutation (c.960delG) was more important as compared to the 3''-UTR mutation (c.2360G>A). Lambs homozygous for the c.960delG mutation grew more slowly than those with other MSTN genotypes, but had the least fat and the largest muscle mass. Only c.960delG showed dominance effects.     

Antibody expressing pea seeds as fodder for prevention of gastrointestinal parasitic infections in chickens

Background

Coccidiosis caused by protozoans of genus Eimeria is a chicken parasitic disease of great economical importance. Conventional disease control strategies depend on vaccination and prophylactic use of anticoccidial drugs. Alternative solution to prevent and treat coccidiosis could be provided by passive immunization using orally delivered neutralizing antibodies. We investigated the possibility to mitigate the parasitic infection by feeding poultry with antibody expressing transgenic crop seeds.

Results

Using the phage display antibody library, we generated a panel of anti-Eimeria scFv antibody fragments with high sporozoite-neutralizing activity. These antibodies were expressed either transiently in agrobacteria-infiltrated tobacco leaves or stably in seeds of transgenic pea plants. Comparison of the scFv antibodies purified either from tobacco leaves or from the pea seeds demonstrated no difference in their antigen-binding activity and molecular form compositions. Force-feeding experiments demonstrated that oral delivery of flour prepared from the transgenic pea seeds had higher parasite neutralizing activity in vivo than the purified antibody fragments isolated from tobacco. The pea seed content was found to protect antibodies against degradation by gastrointestinal proteases (>100-fold gain in stability). Ad libitum feeding of chickens demonstrated that the transgenic seeds were well consumed and not shunned. Furthermore, feeding poultry with shred prepared from the antibody expressing pea seeds led to significant mitigation of infection caused both by high and low challenge doses of Eimeria oocysts.

Conclusion

The results suggest that our strategy offers a general approach to control parasitic infections in production animals using cost-effective antibody expression in crop seeds affordable for the animal health market.     

Electrocardiographic study in Ghanaian children with uncomplicated malaria,treated with artesunate-amodiaquine or artemether-lumefantrine

Background

In order to prepare the field site for future interventions, the prevalence of asymptomatic Plasmodium falciparum infection was evaluated in a cohort of children living in Brazzaville. Plasmodium falciparum merozoite surface protein 2 gene (msp2) was used to characterize the genetic diversity and the multiplicity of infection. The prevalence of mutant P. falciparum chloroquine resistance transporter (pfcrt) allele in isolates was also determined.

Methods

Between April and June 2010, 313 children below 10 years of age enrolled in the cohort for malaria surveillance were screened for P. falciparum infection using microscopy and polymerase chain reaction (PCR). The children were selected on the basis of being asymptomatic. Plasmodium falciparum msp2 gene was genotyped by allele-specific nested PCR and the pfcrt K76T mutation was detected using nested PCR followed by restriction endonuclease digestion.

Results

The prevalence of asymptomatic P. falciparum infections was 8.6% and 16% by microscopy and by PCR respectively. Allele typing of the msp2 gene detected 55% and 45% of 3D7 and FC27 allelic families respectively. The overall multiplicity of infections (MOI) was 1.3. A positive correlation between parasite density and multiplicity of infection was found. The prevalence of the mutant pfcrt allele (T76) in the isolates was 92%.

Conclusion

This is the first molecular characterization of P. falciparum field isolates in Congolese children, four years after changing the malaria treatment policy from chloroquine (CQ) to artemisinin-based combination therapy (ACT). The low prevalence of asymptomatic infections and MOI is discussed in the light of similar studies conducted in Central Africa.     

Diagnosis and molecular characteristics of human infections caused by <Emphasis Type="Italic">Anaplasma phagocytophilum</Emphasis> in South Korea

Human granulocytic anaplasmosis (HGA) is a tick borne infection caused by Anaplasma phagocytophilum. HGA cases in South Korea have been identified since the first report in 2014. In this study, we investigated the serological response in 594 clinical samples of patients with acute febrile illness and molecular characteristics of A. phagocytophilum clinical isolates obtained from HGA patients. In serological test for A. phagocytophilum, 7.91% (47/594 cases) were positive for IgG and Ig M and 13 of 47 cases showed seroconversion. In the detection rate of the 16S rRNA, msp2(p44), and ankA, genes were showed 3.68% (14/380 cases) for A. phagocytophilum-specific 16S rRNA gene. Phylogenetic analysis of three clinical isolates demonstrated high sequence similarity (98.58–100%) with A. phagocytophilum 16S rRNA sequences identified from public databases. Analysis of the msp2(p44) gene showed highly variable similarity rates (7.24–98.85%) even within isolated countries and host ranges. These results provide clues into the bacterial characterization of A. phagocytophilum originating from Korean patients, providing useful guidance for treatment and improving clinical outcomes.