Human Hookworm Infection Enhances Mycobacterial Growth Inhibition and Associates With Reduced Risk of Tuberculosis Infection.

Soil-transmitted helminths and Mycobacterium tuberculosis frequently coincide geographically and it is hypothesized that gastrointestinal helminth infection may exacerbate tuberculosis (TB) disease by suppression of Th1 and Th17 responses. However, few studies have focused on latent TB infection (LTBI), which predominates globally. We performed a large observational study of healthy adults migrating from Nepal to the UK (n = 645). Individuals were screened for LTBI and gastrointestinal parasite infections. A significant negative association between hookworm and LTBI-positivity was seen (OR = 0.221; p = 0.039). Hookworm infection treatment did not affect LTBI conversions. Blood from individuals with hookworm had a significantly greater ability to control virulent mycobacterial growth in vitro than from those without, which was lost following hookworm treatment. There was a significant negative relationship between mycobacterial growth and eosinophil counts. Eosinophil-associated differential gene expression characterized the whole blood transcriptome of hookworm infection and correlated with improved mycobacterial control. These data provide a potential alternative explanation for the reduced prevalence of LTBI among individuals with hookworm infection, and possibly an anti-mycobacterial role for helminth-induced eosinophils.

Molecular Characterization of Cryptosporidium Species and Giardia duodenalis from Symptomatic Cambodian Children.

BACKGROUND: In a prospective study, 498 single faecal samples from children aged under 16 years attending an outpatient clinic in the Angkor Hospital for Children, northwest Cambodia, were examined for Cryptosporidium oocysts and Giardia cysts using microscopy and molecular assays. METHODOLOGY/PRINCIPAL FINDINGS: Cryptosporidium oocysts were detected in 2.2% (11/498) of samples using microscopy and in 7.7% (38/498) with molecular tests. Giardia duodenalis cysts were detected in 18.9% (94/498) by microscopy and 27.7% (138/498) by molecular tests; 82% of the positive samples (by either method) were from children aged 1-10 years. Cryptosporidium hominis was the most common species of Cryptosporidium, detected in 13 (34.2%) samples, followed by Cryptosporidium meleagridis in 9 (23.7%), Cryptosporidium parvum in 8 (21.1%), Cryptosporidium canis in 5 (13.2%), and Cryptosporidium suis and Cryptosporidium ubiquitum in one sample each. Cryptosporidium hominis and C. parvum positive samples were subtyped by sequencing the GP60 gene: C. hominis IaA16R6 and C. parvum IIeA7G1 were the most abundant subtypes. Giardia duodenalis was typed using a multiplex real-time PCR targeting assemblages A and B. Assemblage B (106; 76.8% of all Giardia positive samples) was most common followed by A (12.3%) and mixed infections (5.1%). Risk factors associated with Cryptosporidium were malnutrition (AOR 9.63, 95% CI 1.67-55.46), chronic medical diagnoses (AOR 4.51, 95% CI 1.79-11.34) and the presence of birds in the household (AOR 2.99, 95% CI 1.16-7.73); specifically C. hominis (p = 0.03) and C. meleagridis (p<0.001) were associated with the presence of birds. The use of soap was protective against Giardia infection (OR 0.74, 95% CI 0.58-0.95). CONCLUSIONS/SIGNIFICANCE: This is the first report to describe the different Cryptosporidium species and subtypes and Giardia duodenalis assemblages in Cambodian children. The variety of Cryptosporidium species detected indicates both anthroponotic and zoonotic transmission in this population. Interventions to improve sanitation, increase hand washing after defecation and before preparing food and promote drinking boiled water may reduce the burden of these two parasites.

Intestinal parasite infections in symptomatic children attending hospital in Siem Reap, Cambodia.

BACKGROUND: Infections with helminths and other intestinal parasites are an important but neglected problem in children in developing countries. Accurate surveys of intestinal parasites in children inform empirical treatment regimens and can assess the impact of school based drug treatment programmes. There is limited information on this topic in Cambodia. METHODS: In a prospective study of intestinal parasites in symptomatic children attending Angkor Hospital for Children, Siem Reap, Cambodia, April-June 2012, samples were examined by microscopy of a direct and concentrated fecal sample. Two culture methods for hookworm and Strongyloides stercoralis were employed when sufficient sample was received. Demographic, clinical and epidemiological data were collected. PRINCIPAL FINDINGS: We studied 970 samples from 865 children. The median (inter-quartile range) age of the children was 5.4 (1.9-9.2) years, 54% were male. The proportion of children with abdominal pain was 66.8%, diarrhea 34.9%, anemia 12.7% and malnutrition 7.4%. 458 parasitic infections were detected in 340 (39.3%) children. The most common parasites using all methods of detection were hookworm (14.3%), Strongyloides stercoralis (11.6%) and Giardia lamblia (11.2%). Giardia lamblia was most common in children aged 1-5 years, hookworm and Strongyloides stercoralis were more common with increasing age. Hookworm, Strongloides stercoralis and Giardia lamblia were more common in children living outside of Siem Reap town. In a multivariate logistic regression increasing age was associated with all three infections, defecating in the forest for hookworm infection, the presence of cattle for S. stercoralis and not using soap for handwashing for G. lamblia. CONCLUSIONS/SIGNIFICANCE: This study confirms the importance of intestinal parasitic infections in symptomatic Cambodian children and the need for adequate facilities for laboratory diagnosis together with education to improve personal hygiene and sanitation.

Guideline: the laboratory diagnosis of malaria. General Haematology Task Force of the British Committee for Standards in Haematology.

UK National External Quality Assessment Service surveys indicate continuing problems in malaria diagnosis: inaccurate calculation of parasitaemia or failure to estimate it altogether, difficulty distinguishing Plasmodium vivax from P. ovale, reporting malaria parasites when none were present and misidentification of P. falciparum as another species still occur. Therefore, the British Committee for Standards in Haematology Guidelines for the Laboratory Diagnosis of Malaria have been revised. They are intended for use in the UK but may also prove useful in other non-endemic areas. Routine use of thick and thin films is advised for malaria diagnosis. Thick films should be stained using Giemsa or Field stain. Thin films should be stained with Giemsa stain or Leishman stain. Thick films should be examined by two observers, each viewing a minimum of 200 high power fields. If thick films are positive, the species should be determined by examination of a thin film. In the case of P. falciparum or P. knowlesi infection, the percentage of parasitized cells or the number of parasites per microlitre (/µl) should be estimated and reported. Rapid diagnostic tests (RDTs) for malarial antigen cannot replace microscopy but are indicated as a supplementary test when malaria diagnosis is performed by relatively inexperienced staff. Malaria RDTs are negative in babesiosis.

Whole-genome sequencing of Trypanosoma brucei reveals introgression between subspecies that is associated with virulence.

UNLABELLED: Human African trypanosomiasis is caused by two subspecies of Trypanosoma brucei. Trypanosoma brucei rhodesiense is found in East Africa and frequently causes acute disease, while Trypanosoma brucei gambiense is found in West Africa and is associated with chronic disease. Samples taken from a single focus of a Ugandan outbreak of T. b. rhodesiense in the 1980s were associated with either chronic or acute disease. We sequenced the whole genomes of two of these isolates, which showed that they are genetically distinct from each other. Analysis of single nucleotide polymorphism markers in a panel of 31 Ugandan isolates plus 32 controls revealed a mixture of East African and West African haplotypes, and some of these haplotypes were associated with the different virulence phenotypes. It has been shown recently that T. b. brucei and T. b. rhodesiense populations undergo genetic exchange in natural populations. Our analysis showed that these strains from the Ugandan epidemic were intermediate between the reference genome sequences of T. b. gambiense and T. b. brucei and contained haplotypes that were present in both subspecies. This suggests that the human-infective subspecies of T. brucei are not genetically isolated, and our data are consistent with genomic introgression between East African and West African T. b. brucei subspecies. This has implications for the control of the parasite, the spread of drug resistance, and understanding the variation in virulence and the emergence of human infectivity. IMPORTANCE: We present a genetic study of the acute form of "sleeping sickness" caused by the protozoan parasite Trypanosoma brucei rhodesiense from a single outbreak in Uganda. This represents an advance in our understanding of the relationship between the T. b. rhodesiense and Trypanosoma brucei gambiense subspecies that have previously been considered geographically distinct. Our data suggest that introgression of West African-derived T. brucei haplotypes may be associated with differences in disease presentation in the East African disease. These findings are not only of scientific interest but also important for parasite control, as they suggest that the human-infective T. brucei subspecies are not genetically isolated.

Multiorgan dysfunction caused by travel-associated African trypanosomiasis.

We describe a case of multiorgan dysfunction secondary to Trypanosoma brucei rhodesiense infection acquired on safari in Zambia. This case was one of several recently reported to ProMED-mail in persons who had traveled to this region. Trypanosomiasis remains rare in travelers but should be considered in febrile patients who have returned from trypanosomiasis-endemic areas of Africa.

Why does HIV infection not lead to disseminated strongyloidiasis?

We investigated the hypothesis that host immunosuppression due to advancing human immunodeficiency virus (HIV) disease favors the direct development of infective larvae of Strongyloides stercoralis, which may facilitate hyperinfection and, hence, disseminated strongyloidiasis. To do this, we sought correlations between the immune status of the subjects and the development of S. stercoralis infections. Among 35 adults, there were significant negative rank correlations between CD4+ cell counts and the proportions of free-living male and female worms. Thus, in individuals with preserved immune function, direct development of S. stercoralis is favored, whereas, in individuals with lesser immune function, indirect development is relatively more common. These results may explain the notable absence of disseminated strongyloidiasis in advanced HIV disease. Because disseminated infection requires the direct development of infective larvae in the gut, the observed favoring of indirect development in individuals immunosuppressed by advancing HIV disease is not consistent with the promotion of disseminated infection.

African trypanosomiasis in travelers returning to the United Kingdom.

Two returning safari tourists with African trypanosomiasis were admitted to the Hospital for Tropical Diseases, London, in a 3-day period, compared with six cases in the previous 14 years. We describe the clinical features, diagnosis, and problems encountered in accessing appropriate therapy, and discuss the potential for emergence of this disease in increasingly adventurous international travelers.