Emerging parasitic disease mimics the symptoms of visceral leishmaniasis in people

WHAT:

A new study published this week online in

Emerging Infectious Diseases

suggests that transmission of a protozoan parasite from insects may also cause leishmaniasis-like symptoms in people. The parasite, however, does not respond to treatment with standard leishmaniasis drugs. The research was conducted by scientists at the Federal Universities of Sergipe and São Carlos, the University of São Paulo, and the Oswaldo Cruz Foundation, all in Brazil, along with investigators at the National Institute of Allergy and Infectious Diseases (NIAID), part of the U.S. National Institutes of Health.

Leishmaniasis is a parasitic disease found in parts of the tropics, subtropics, and southern Europe. It is classified as a neglected tropical disease and is often transmitted by the bite of some sandflies. The most common forms of leishmaniasis are are cutaneous, which causes skin sores, and visceral, which affects several internal organs (usually spleen, liver, and bone marrow). According to the World Health Organization, each year between 50,000 and 90,000 people become sick with visceral leishmaniasis (kala-azar), a form of the disease that attacks the internal organs and is fatal in more than 95 percent of cases left untreated. During the last several decades, researchers have described rare cases of patients co-infected with both

Leishmania

and other groups of protozoan parasites that usually infect insects, including

Crithidia

. The current study of parasites isolated from a Brazilian patient confirms that

Crithidia

parasites also can infect people.

The 63-year old patient initially sought treatment for the symptoms of visceral leishmaniasis, including weight loss, fever, anemia, and an enlarged liver and spleen. However, after eight months of standard leishmaniasis treatment, the patient’s symptoms had not improved. The patient developed widespread skin lesions with poorly defined edges (unlike the small lesions with well-defined edges that sometimes appear after treatment for visceral leishmaniasis) and ultimately died.

To determine the cause of disease, researchers cultured parasites taken from the patient’s bone marrow and skin lesions, sequenced their genomes, and discovered that the parasites were not closely related to known disease-causing

Leishmania

parasites. Instead, they were more closely related to

Crithidia

fasciculata, a parasite that usually colonizes mosquitoes. To confirm that these

Crithidia

parasites could infect mammals, the researchers exposed mice to the parasites isolated from the patient, both intravenously and by injection into the skin, and found that both types of parasite infected the liver. The parasites collected from the patient’s skin also caused skin lesions in the mice.

The study raises concerns that the Brazilian patient might not be an isolated case. If

Crithidia

infections represent an emerging infectious disease in people, there will be an urgent need to develop novel effective treatments, the researchers write. They expressed concern that the disease may be mosquito-borne because

Anopheles

and

Culex

mosquitoes can host the

Crithidia

parasite. More research will be needed to find other human cases, confirm the parasite’s range and host species, and discover potential treatments, the authors note.

###

ARTICLE:

Maruyama

et al

. Non-

leishmania

parasite in fatal visceral leishmaniasis-like disease, Brazil.

Emerging Infectious Diseases

DOI: 10.3201/eid2511.181548 (2019).

WHO:

José M. Ribeiro, M.D., Ph.D., Chief of the Vector Biology Section in NIAID’s Laboratory of Malaria and Vector Research, is available for comment on this study.

CONTACT:

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[email protected]

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NIAID conducts and supports research–at NIH, throughout the United States, and worldwide–to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing and treating these illnesses. News releases, fact sheets and other NIAID-related materials are available on the NIAID website.

About the National Institutes of Health (NIH):

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http://www.

nih.

gov/

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