Strongyloidiasis is a worm infection which affects more than 100 million people, mostly in Africa, Asia and Latin America, and can cause severe illness in people with reduced immunity. In the UK, the number of people with Strongyloides is not known.

At Imperial College Healthcare NHS Trust (ICHNT) , screening for Stongyloides has recently been introduced as a standard-of-care for all patients undergoing BMT.

In this study, investigators will perform two cross-sectional surveys and report the prevalence of Strongyloides in BMT recipients at ICHNT , as well as comparing clinical outcomes before/after the introduction of routine testing.

Strongyloidiasis is a worm infection which affects more than 100 million people, mostly in Africa, Asia and Latin America. Infection can persist for decades, and usually causes mild symptoms. In some people with reduced immune systems (for example those who have bone marrow transplantation), the worms can multiply and cause severe illness and death.

In the UK, the number of people with Strongyloides is not known. However, in many other non-tropical countries, rates are high in immigrant populations (including those who are having bone marrow transplantation, BMT).

At ICHNT, screening for Stongyloides has recently been introduced as a standard-of-care for all patients undergoing BMT. All adult patients with forthcoming BMT at ICHNT will now be screened. Additionally, any patients who have already undergone BMT in the last two years will be screened as part of a look-back exercise as part of their clinical care.

In this study, investigators will perform two cross-sectional surveys. Those who underwent BMT between Jun 2018 - July 2020 will form a 'pre-screening group', and those between July 2020 - July 2021 will form a 'screened group'. It is anticipated that 320 participants will be included in the pre-screening group and 160 in the screened-group (total 480).

Data will be collected retrospectively and the prevalence of Strongyloides in BMT recipients at ICHNT will be reported. Comparison of clinical outcomes between the first and second groups will be undertaken, in order to determine whether the introduction of screening has had an impact.

Inclusion Criteria:

• Adult patients
• Under care of Haematology at ICHNT
• Undergoing BMT Jun 2018 - July 2020 ('pre-screening group') or July 2020 - July 2021 ('screened group')

Exclusion Criteria:

• Age < 18 years (i.e. managed as paediatric BMT)
• Previous BMT but no Strongyloides serology result available at the time of data collection

Individuals under the care of Haematology at ICHNT