Soil-Transmitted Helminths in Children in a Remote Aboriginal Community in the Northern Territory: Hookworm is Rare but Strongyloides stercoralis and Trichuris trichiura Persist

Human strongyloidiasis: complexities and pathways forward

Strongyloidiasis is a World Health Organization neglected tropical disease usually caused by Strongyloides stercoralis, a parasitic worm with a complex life cycle. Globally, 300-600 million people are infected through contact with fecally contaminated soil. An autoinfective component of the life cycle can lead to chronic infection that may be asymptomatic or cause long-term symptoms, including malnourishment in children. Low larval output can limit the sensitivity of detection in stool, with serology being effective but less sensitive in immunocompromise. Host immunosuppression can trigger catastrophic, fatal hyperinfection/dissemination, where large numbers of larvae pierce the bowel wall and disseminate throughout the organs. Stable disease is effectively treated by single-dose ivermectin, with disease in immunocompromised patients treated with multiple doses. Strategies for management include raising awareness, clarifying zoonotic potential, the development and use of effective diagnostic tests for epidemiological studies and individual diagnosis, and the implementation of treatment programs with research into therapeutic alternatives and medication safety.

Long-term outcomes of ivermectin-albendazole versus albendazole alone against soil-transmitted helminths: Results from randomized controlled trials in Lao PDR and Pemba Island, Tanzania

BACKGROUND

Preventive chemotherapy is the cornerstone of soil-transmitted helminth (STH) control. Long-term outcomes and adequate treatment frequency of the recently recommended albendazole-ivermectin have not been studied to date.

METHODOLOGY/PRINCIPAL FINDINGS

Double-blind randomized controlled trials were conducted in Lao PDR, Pemba Island, Tanzania and Côte d'Ivoire between 2018 and 2020 to evaluate the efficacy and safety of ivermectin-albendazole versus albendazole-placebo in Trichuris trichiura-infected individuals aged 6 to 60. In the framework of this study, in Lao PDR 466 and 413 participants and on Pemba Island, 558 and 515 participants were followed-up six and 12 months post-treatment, respectively. From each participant at least one stool sample was processed for Kato-Katz diagnosis and cure rates (CRs), egg reduction rates (ERRs) and apparent reinfection rates were calculated. If found helminth-positive at six months, participants were re-treated according to their allocated treatment. Long-term outcomes against T. trichiura based on CRs and ERRs of ivermectin-albendazole compared to albendazole were significantly higher at six months in Lao PDR (CR, 65.8 vs 13.4%, difference; 52.4; 95% CI 45.0-60.0; ERRs, 99.0 vs 79.6, difference 19.4; 95% CI 14.4-24.4) and Pemba Island (CR, 17.8 vs 1.4%, difference; 16.4; 95% CI 11.6-21.0; ERRs, 84.9 vs 21.2, difference 63.8; 95% CI 50.6-76.9) and also at 12 months in Lao PDR (CR, 74.0 vs 23.4%, difference; 50.6; 95% CI 42.6-61.0; ERRs, 99.6 vs 91.3, difference 8.3; 95% CI 5.7-10.8) and Pemba Island (CR, 19.5 vs 3.4%, difference; 16.1; 95% CI 10.7-21.5; ERRs, 92.9 vs 53.6, difference 39.3; 95% CI 31.2-47.4) respectively. Apparent reinfection rates with T. trichiura were considerably higher on Pemba Island (100.0%, 95% CI, 29.2-100.0) than in Lao PDR (10.0%, 95% CI, 0.2-44.5) at 12 months post-treatment for participants treated with albendazole alone.

CONCLUSIONS/SIGNIFICANCE

The long-term outcomes against T. trichiura of ivermectin-albendazole are superior to albendazole in terms of CRs and ERRs and in reducing infection intensities. Our results will help to guide decisions on how to best use ivermectin-albendazole in the context of large-scale PC programs tailored to the local context to sustainably control STH infections.

TRIAL REGISTRATION

ClinicalTrials.gov registered with clinicaltrials.gov, reference: NCT03527732, date assigned: 17 May 2018.

Comparison of Profiles of First Nations and Non-First Nations Children With Bronchiectasis Over Two 5-Year Periods in the Northern Territory, Australia

BACKGROUND

Although the burden of bronchiectasis is recognized globally, pediatric data are limited, particularly on trends over the years. Also, no published data exists regarding whether vitamin D deficiency or insufficiency and human T-cell lymphotropic virus type 1 (HTLV-1) infection, both found to be related to severe bronchiectasis in First Nations adults, also are important in children with bronchiectasis.

RESEARCH QUESTION

Among children with bronchiectasis, (1) have the clinical and BAL profiles changed between two 5-year periods (period 1, 2007-2011; period 2, 2012-2016) and (b) are vitamin D deficiency or insufficiency, HTLV-1 infection, or both associated with radiologic severity of bronchiectasis?

STUDY DESIGN AND METHODS

We analyzed the data from children with bronchiectasis prospectively enrolled at Royal Darwin Hospital, Australia, at the first diagnosis; that is, no child was included in both periods. Data collected include demographics, BAL, bloods, and high-resolution CT scan of the chest evaluated using the Bhalla and modified Bhalla scores.

RESULTS

The median age of the 299 children was 2.2 years (interquartile range, 1.5-3.7 years). One hundred sixty-eight (56%) were male and most were First Nations (92%). Overall, bronchiectasis was high over time, particularly among First Nations children. In the later period, numbers of non-First Nations children more than tripled, but did not reach statistical significance. In period 2 compared with period 1, fewer First Nations children demonstrated chronic cough (period 1, 61%; period 2, 47%; P = .03), were younger, First Nations children were less likely to have received azithromycin (period 1, 42%; period 2, 21%; P < .001), and the BAL fluid of First Nations children showed lower Haemophilus influenzae and Moraxella catarrhalis infection. HTLV-1 infection was not detected, and vitamin D deficiency or insufficiency did not correlate with severity of bronchiectasis.

INTERPRETATION

Bronchiectasis remains high particularly among First Nations children. Important changes in their profiles that arguably reflect improvements were present, but overall, the profiles remained similar. Although vitamin D deficiency was uncommon, its role in children with bronchiectasis requires further evaluation. HTLV-1 infection was nonexistent and is unlikely to play any role in First Nations children with bronchiectasis.

Housing conditions and health in Indigenous Australian communities: current status and recent trends

Ensuring sufficient and adequately maintained housing in Indigenous Australian communities remains an ongoing policy challenge for government, with major implications for the health of Indigenous Australians. This study sought to characterise the current status of housing conditions experienced by Indigenous Australians, with special reference to the Northern Territory. The assessment examined a range of indicators relating to crowding, dwelling condition, 'health hardware', and provision of maintenance and repairs. While acknowledging data deficiencies and inconsistencies, the analysis produced mixed results. There was evidence of a reduction in crowding but little observable improvement in the provision of maintenance and repairs. Some housing-related health outcomes have shown improvement, though these have tended to coincide with mass treatment campaigns. Achieving the goal of healthy homes - and ultimately closing the gap on Indigenous disadvantage - requires further investment in new houses that are appropriately designed and constructed, alongside an increased emphasis on cyclical maintenance.

Seropositivity and geographical distribution of Strongyloides stercoralis in Australia: A study of pathology laboratory data from 2012-2016

Background

There are no national prevalence studies of Strongyloides stercoralis infection in Australia, although it is known to be endemic in northern Australia and is reported in high risk groups such as immigrants and returned travellers. We aimed to determine the seropositivity (number positive per 100,000 of population and percent positive of those tested) and geographical distribution of S. stercoralis by using data from pathology laboratories.

Methodology

We contacted all seven Australian laboratories that undertake Strongyloides serological (ELISA antibody) testing to request de-identified data from 2012–2016 inclusive. Six responded. One provided positive data only. The number of people positive, number negative and number tested per 100,000 of population (Australian Bureau of Statistics data) were calculated including for each state/territory, each Australian Bureau of Statistics Statistical Area Level 3 (region), and each suburb/town/community/locality. The data was summarized and expressed as maps of Australia and Greater Capital Cities.

Principal findings

We obtained data for 81,777 people who underwent serological testing for Strongyloides infection, 631 of whom were from a laboratory that provided positive data only. Overall, 32 (95% CI: 31, 33) people per 100,000 of population were seropositive, ranging between 23/100,000 (95% CI: 19, 29) (Tasmania) and 489/100,000 population (95%CI: 462, 517) (Northern Territory). Positive cases were detected across all states and territories, with the highest (260-996/100,000 and 17–40% of those tested) in regions across northern Australia, north-east New South Wales and north-west South Australia. Some regions in Greater Capital Cities also had a high seropositivity (112-188/100,000 and 17–20% of those tested). Relatively more males than females tested positive. Relatively more adults than children tested positive. Children were under-represented in the data.

Conclusions/Significance

The study confirms that substantial numbers of S. stercoralis infections occur in Australia and provides data to inform public health planning.

Strongyloides stercoralis, a parasitic roundworm, is endemic in many countries world-wide. In Australia, groups at risk for strongyloidiasis include Aboriginal and/or Torres Strait Islander people, who acquired this parasite locally, and immigrants and returned travellers who acquired the infection outside Australia. We obtained deidentified results of ELISA IgG antibody tests for Strongyloides from diagnostic pathology laboratories during 2012 to 2016 and calculated the number of people who were positive at least once and the number who never had a positive result. We drew maps showing the number positive per 100,000 of population, the percent positive of those tested, and the number tested/100,000 for each region and the number positive in each suburb of residence according to the Australian Bureau of Statistics. The highest seropositivity (260-996/100,000 of population) was in Northern Australia, north-west South Australia and north-east New South Wales where many Aboriginal and Torres Strait Islander people live in remote communities. There were also some regions in Greater Capital Cities with a high number of people positive per 100,000 of population (112-188/100,000), likely reflecting higher populations of immigrants and returned travellers who were infected outside Australia.

Enteric pathogen infection and consequences for child growth in young Aboriginal Australian children: a cross-sectional study

BACKGROUND

To determine the prevalence of enteric infections in Aboriginal children aged 0-2 years using conventional and molecular diagnostic techniques and to explore associations between the presence of pathogens and child growth.

METHODS

Cross-sectional analysis of Aboriginal children (n = 62) residing in a remote community in Northern Australia, conducted from July 24th - October 30th 2017. Stool samples were analysed for organisms by microscopy (directly in the field and following fixation and storage in sodium-acetate formalin), and by qualitative PCR for viruses, bacteria and parasites and serology for Strongyloides-specific IgG. Child growth (height and weight) was measured and z scores calculated according to WHO growth standards.

RESULTS

Nearly 60% of children had evidence for at least one enteric pathogen in their stool (37/62). The highest burden of infection was with adenovirus/sapovirus (22.9%), followed by astrovirus (9.8%) and Cryptosporidium hominis/parvum (8.2%). Non-pathogenic organisms were detected in 22.5% of children. Ten percent of children had diarrhea at the time of stool collection. Infection with two or more pathogens was negatively associated with height for age z scores (- 1.34, 95% CI - 2.61 to - 0.07), as was carriage of the non-pathogen Blastocystis hominis (- 2.05, 95% CI - 3.55 to - 0.54).

CONCLUSIONS

Infants and toddlers living in this remote Northern Australian Aboriginal community had a high burden of enteric pathogens and non-pathogens. The association between carriage of pathogens/non-pathogens with impaired child growth in the critical first 1000 days of life has implications for healthy child growth and development and warrants further investigation. These findings have relevance for many other First Nations Communities that face many of the same challenges with regard to poverty, infections, and malnutrition.

HTLV-I and Strongyloides in Australia: The worm lurking beneath

Strongyloidiasis and HTLV-I (human T-lymphotropic virus-1) are important infections that are endemic in many countries around the world with an estimated 370 million infected with Strongyloides stercoralis alone, and 5-10 million with HTVL-I. Co-infections with these pathogens are associated with significant morbidity and can be fatal. HTLV-I infects T-cells thus causing dysregulation of the immune system which has been linked to dissemination and hyperinfection of S. stercoralis leading to bacterial sepsis which can result in death. Both of these pathogens are endemic in Australia primarily in remote communities in Queensland, the Northern Territory, and Western Australia. Other cases in Australia have occurred in immigrants and refugees, returned travellers, and Australian Defence Force personnel. HTLV-I infection is lifelong with no known cure. Strongyloidiasis is a long-term chronic disease that can remain latent for decades, as shown by infections diagnosed in prisoners of war from World War II and the Vietnam War testing positive decades after they returned from these conflicts. This review aims to shed light on concomitant infections of HTLV-I with S. stercoralis primarily in Australia but in the global context as well.

Whipworm and roundworm infections

Trichuriasis and ascariasis are neglected tropical diseases caused by the gastrointestinal dwelling nematodes Trichuris trichiura (a whipworm) and Ascaris lumbricoides (a roundworm), respectively. Both parasites are staggeringly prevalent, particularly in tropical and subtropical areas, and are associated with substantial morbidity. Infection is initiated by ingestion of infective eggs, which hatch in the intestine. Thereafter, T. trichiura larvae moult within intestinal epithelial cells, with adult worms embedded in a partially intracellular niche in the large intestine, whereas A. lumbricoides larvae penetrate the gut mucosa and migrate through the liver and lungs before returning to the lumen of the small intestine, where adult worms dwell. Both species elicit type 2 anti-parasite immunity. Diagnosis is typically based on clinical presentation (gastrointestinal symptoms and inflammation) and the detection of eggs or parasite DNA in the faeces. Prevention and treatment strategies rely on periodic mass drug administration (generally with albendazole or mebendazole) to at-risk populations and improvements in water, sanitation and hygiene. The effectiveness of drug treatment is very high for A. lumbricoides infections, whereas cure rates for T. trichiura infections are low. Novel anthelminthic drugs are needed, together with vaccine development and tools for diagnosis and assessment of parasite control in the field.

Opportunistic Mapping of Strongyloides stercoralis and Hookworm in Dogs in Remote Australian Communities

Both Strongyloides stercoralis and hookworms are common soil-transmitted helminths in remote Australian communities. In addition to infecting humans, S. stercoralis and some species of hookworms infect canids and therefore present both environmental and zoonotic sources of transmission to humans. Currently, there is limited information available on the prevalence of hookworms and S. stercoralis infections in dogs living in communities across the Northern Territory in Australia. In this study, 274 dog faecal samples and 11 faecal samples of unknown origin were collected from the environment and directly from animals across 27 remote communities in Northern and Central Australia. Samples were examined using real-time polymerase chain reaction (PCR) analysis for the presence of S. stercoralis and four hookworm species: Ancylostoma caninum, Ancylostoma ceylanicum, Ancylostoma braziliense and Uncinaria stenocephala. The prevalence of S. stercoralis in dogs was found to be 21.9% (60/274). A. caninum was the only hookworm detected in the dog samples, with a prevalence of 31.4% (86/274). This study provides an insight into the prevalence of S. stercoralis and hookworms in dogs and informs future intervention and prevention strategies aimed at controlling these parasites in both dogs and humans. A "One Health" approach is crucial for the prevention of these diseases in Australia.

A Case for Using Genomics and a Bioinformatics Pipeline to Develop Sensitive and Species-Specific PCR-Based Diagnostics for Soil-Transmitted Helminths

The balance of expense and ease of use vs. specificity and sensitivity in diagnostic assays for helminth disease is an important consideration, with expense and ease often winning out in endemic areas where funds and sophisticated equipment may be scarce. In this review, we argue that molecular diagnostics, specifically new assays that have been developed with the aid of next-generation sequence data and robust bioinformatic tools, more than make up for their expense with the benefit of a clear and precise assessment of the situation on the ground. Elimination efforts associated with the London Declaration and the World Health Organization (WHO) 2020 Roadmap have resulted in areas of low disease incidence and reduced infection burdens. An accurate assessment of infection levels is critical for determining where and when the programs can be successfully ended. Thus, more sensitive assays are needed in locations where elimination efforts are approaching a successful conclusion. Although microscopy or more general PCR targets have a role to play, they can mislead and cause study results to be confounded. Hyper-specific qPCR assays enable a more definitive assessment of the situation in the field, as well as of shifting dynamics and emerging diseases.

Detection of classic and cryptic Strongyloides genotypes by deep amplicon sequencing: A preliminary survey of dog and human specimens collected from remote Australian communities

Strongyloidiasis is caused by the human infective nematodes Strongyloides stercoralis, Strongyloides fuelleborni subsp. fuelleborni and Strongyloides fuelleborni subsp. kellyi. The zoonotic potential of S. stercoralis and the potential role of dogs in the maintenance of strongyloidiasis transmission has been a topic of interest and discussion for many years. In Australia, strongyloidiasis is prevalent in remote socioeconomically disadvantaged communities in the north of the continent. Being an isolated continent that has been separated from other regions for a long geological period, description of diversity of Australian Strongyloides genotypes adds to our understanding of the genetic diversity within the genus. Using PCR and amplicon sequencing (Illumina sequencing technology), we sequenced the Strongyloides SSU rDNA hyper-variable I and hyper-variable IV regions using Strongyloides-specific primers, and a fragment of the mtDNA cox1 gene using primers that are broadly specific for Strongyloides sp. and hookworms. These loci were amplified from DNA extracted from Australian human and dog faeces, and one human sputum sample. Using this approach, we confirm for the first time that potentially zoonotic S. stercoralis populations are present in Australia, suggesting that dogs represent a potential reservoir of human strongyloidiasis in remote Australian communities.

Argument for Inclusion of Strongyloidiasis in the Australian National Notifiable Disease List

Strongyloidiasis is an infection caused by the helminth, Strongyloides stercoralis. Up to 370 million people are infected with the parasite globally, and it has remained endemic in the Indigenous Australian population for many decades. Strongyloidiasis has been also reported in other Australian populations. Ignorance of this disease has caused unnecessary costs to the government health system, and been detrimental to the Australian people's health. This manuscript addresses the 12 criteria required for a disease to be included in the Australian National Notifiable Disease List (NNDL) under the National Health Security Act 2007 (Commonwealth). There are six main arguments that provide compelling justification for strongyloidiasis to be made nationally notifiable and added to the Australian NNDL. These are: The disease is important to Indigenous health, and closing the health inequity gap between Indigenous and non-Indigenous Australians is a priority; a public health response is required to detect cases of strongyloidiasis and to establish the true incidence and prevalence of the disease; there is no alternative national surveillance system to gather data on the disease; there are preventive measures with high efficacy and low side effects; data collection is feasible as cases are definable by microscopy, PCR, or serological diagnostics; and achievement of the Sustainable Development Goal (SDG) # 6 on clean water and sanitation.