Strongyloidiasis in Auckland: A ten-year retrospective study of diagnosis, treatment and outcomes of a predominantly Polynesian and Fijian migrant cohort

Background Strongyloides stercoralis is not endemic in Aotearoa New Zealand (AoNZ). However, approximately one third of Auckland residents are born in endemic countries. This study aimed to describe the epidemiology and management of strongyloidiasis in Auckland, with a focus on migrants from Pacific Island Countries and Territories.Methods This study retrospectively reviewed clinical, laboratory and pharmacy records data for all people diagnosed with strongyloidiasis in the Auckland region between July 2012 and June 2022. People with negative Strongyloides serology were included to estimate seropositivity rate by country of birth.Findings Over ten years, 691 people were diagnosed with strongyloidiasis. Most diagnoses were made by serology alone (441, 64%). The median age was 63 years (range 15-92), 500 (72%) were male, and the majority were born in Polynesia (350, 51%), Fiji (130, 19%) or were of Pasifika ethnicity (7%). Twelve participants (1.7%) had severe strongyloidiasis at diagnosis. The total proportion treated with ivermectin was only 70% (484/691), with no differences between immunocompromised and immunocompetent participants, nor by ethnicity. The outcome of treatment (based on a combination of serology and/or eosinophilia and/or stool microscopy) could only be determined in 50% of the treated cohort. One participant failed treatment with ivermectin, experiencing recurrent strongyloidiasis, and another participant died in association with severe strongyloidiasis. The rate of 'positive' Strongyloides serology was highest among participants born in Samoa (48%), Fiji (39%), and Southeast Asian countries (34%).Findings Over ten years, 691 people were diagnosed with strongyloidiasis. Most diagnoses were made by serology alone (441, 64%). The median age was 63 years (range 15-92), 500 (72%) were male, and the majority were born in Polynesia (350, 51%), Fiji (130, 19%) or were of Pasifika ethnicity (7%). Twelve participants (1.7%) had severe strongyloidiasis at diagnosis. The total proportion treated with ivermectin was only 70% (484/691), with no differences between immunocompromised and immunocompetent participants, nor by ethnicity. The outcome of treatment (based on a combination of serology and/or eosinophilia and/or stool microscopy) could only be determined in 50% of the treated cohort. One participant failed treatment with ivermectin, experiencing recurrent strongyloidiasis, and another participant died in association with severe strongyloidiasis. The rate of 'positive' Strongyloides serology was highest among participants born in Samoa (48%), Fiji (39%), and Southeast Asian countries (34%).Findings Over ten years, 691 people were diagnosed with strongyloidiasis. Most diagnoses were made by serology alone (441, 64%). The median age was 63 years (range 15-92), 500 (72%) were male, and the majority were born in Polynesia (350, 51%), Fiji (130, 19%) or were of Pasifika ethnicity (7%). Twelve participants (1.7%) had severe strongyloidiasis at diagnosis. The total proportion treated with ivermectin was only 70% (484/691), with no differences between immunocompromised and immunocompetent participants, nor by ethnicity. The outcome of treatment (based on a combination of serology and/or eosinophilia and/or stool microscopy) could only be determined in 50% of the treated cohort. One participant failed treatment with ivermectin, experiencing recurrent strongyloidiasis, and another participant died in association with severe strongyloidiasis. The rate of 'positive' Strongyloides serology was highest among participants born in Samoa (48%), Fiji (39%), and Southeast Asian countries (34%).Interpretation Strongyloidiasis was common and under-treated in Auckland during the study period. Clinicians should have a low threshold for considering strongyloidiasis in migrants from endemic countries, including Polynesia and Fiji. Strongyloides stercoralis is endemic to most tropical and subtropical countries, and causes potentially life-long infection of the gastrointestinal tract. Strongyloidiasis can occasionally cause life-threatening illness, particularly in immunocompromised people, and often years after the initial infection. Very little is known about the burden of strongyloidiasis in Oceania, particularly in the Pacific Island Countries and Territories of Polynesia and Fiji. Auckland (New Zealand) is home to a large population of migrants from Polynesia and Fiji, and clinicians in Auckland frequently treat strongyloidiasis.This study describes a cohort of 691 people diagnosed with strongyloidiasis in Auckland between 2012 and 2022. Only 70% of people in this cohort received treatment. The proportion receiving treatment did not differ significantly among people with the highest risk of severe strongyloidiasis. In addition, high rates of positive Strongyloides serology were found among people born in Samoa and Fiji, which were comparable to seropositivity among migrants from other 'high burden' countries (South East Asia). In addition to identifying a need to improve management of strongyloidiasis in Auckland, this study suggests the burden of strongyloidiasis in Polynesia and Fiji may be higher than previously suggested.