Filariform larva of Strongyloides. Strongyloidiasis is a worm infection of the gut which can be treated with Ivermectin.

As we move further into 2019, reflection on the successes and challenges of 2018 enables us to better understand the landscape of tropical medicine, prioritize initiatives that capitalize on last year’s successes, and identify areas for renewed focus.

As Editor-in-Chief of Tropical Diseases, Travel Medicine and Vaccines, I am delighted to post this series of blogs, which will count down five hot topics in tropical medicine that made an impact in our field last year.

Approval of Ivermectin for strongyloidiasis by Health Canada

In 2015, the Nobel Prize in Physiology or Medicine was jointly awarded to Drs. William C. Campbell and Satoshi Ōmura for their discovery of the “avermectin” family of compounds, from which ivermectin is derived. Ivermectin acts by interfering with worm neural and muscle cells, ultimately leading to paralysis. Ivermectin is licensed for human use in several countries for a variety of parasitic indications, particularly worm infections called “onchocerciasis” and “strongyloidiasis”. Of these infections, the more common condition in Western countries like Canada is strongyloidiasis, a worm infection of the gut.

It is estimated that at least 2.5 million new Canadians suffer from strongyloidiasis

Symptoms  may only become obvious decades after exposure but  chronic symptoms can include chronic rash, stomach pain and acid reflux that is unresponsive to acid suppression pills. Lifelong infections can result in a dangerous syndrome called “hyperinfection” when a person’s immune response becomes impaired by medications such as steroids, chemotherapy agents, or other medicines used in the treatment of autoimmune diseases.

Strongyloidiasis is particularly seen among migrants and refugees, who account for almost a quarter of the total Canadian population. Of the 7.5 million foreign-born Canadians representing the country’s ethnocultural diversity, 85% have emigrated from countries where strongyloidiasis could have been acquired.

In migrants to Canada, studies have shown high rates of strongyloidiasis, with up to 77% of refugees from Cambodia and 12% of refugees from Vietnam having the infection. Additionally, strongyloidiasis is consistently among the top five causes of illness in studies of new migrants being cared for at specialized post-travel medical centres. It is estimated that at least 2.5 million new Canadians suffer from strongyloidiasis.

State of Affairs in Canada Prior to 2018

There is a known lack of access to essential anti-worm drugs in Canada. Effective medications are neither licensed nor marketed in the country for the vast majority of neglected tropical diseases (NTDs) listed by the WHO. To obtain ivermectin prior to 2018, physicians had to apply to Health Canada’s “Special Access Programme” (SAP), which provides individual approvals for drugs that are not licensed in the country. Accessibility of “SAP” medications remains limited, with at least a one-week delay between the application to Health Canada and receipt of the drug.

The combination of lack of access to ivermectin, increasing immigration from high-risk countries and the ever-expanding use of immunosuppressing medicines, culminated in frequent cases of death due to “hyperinfection” strongyloidiasis across Canada. These occurrences motivated the Committee to Advise on Tropical Medicine and Travel (CATMAT), an external advisory body to the Public Health Agency of Canada, to draft national guidelines on the subject in order to reduce the health risks of strongyloidiasis.

Undoubtedly, this approval will facilitate more timely access to ivermectin for treatment of strongyloidiasis

What Changed in 2018?

On September 10, 2018, Merck & Co., Inc. was granted licensure of ivermectin (Stromectol®) by Health Canada, which now allows the drug to be marketed and maintained on pharmacy formularies. Undoubtedly, this approval will facilitate more timely access to ivermectin for treatment of strongyloidiasis, which is likely to reduce related health burden, particularly as this drug may now be included in pre- screening programs designed to detect infections before initiation of immunosuppressing medications (e.g., before organ transplant or cancer chemotherapy).

A potential drawback of ivermectin approval in Canada remains the financial constraints facing patients who lack public or private drug coverage, for whom the medication will now cost $7 Canadian per pill, whereas via Health Canada’s Special Access Programme, the drug was dispensed free of charge.

Ivermectin has had a major impact on the burden of neglected tropical diseases on the global scale. Its approval for licensure and marketing In Canada has allowed doctors caring for patients with many parasitic infections, including strongyloidiasis, to able to appropriately treat them. This represents a promising milestone for Canadians, and a potential example for other countries to likewise expand accessibility to essential anti-parasitic medications.