Emerging parasitic disease mimics the symptoms of visceral leishmaniasis (kala-azar) in people

New Delhi, 01 October 2019. A new study 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 study Non-Leishmania
Parasite in Fatal Visceral Leishmaniasis–like Disease, Brazil was published
this week online in Emerging Infectious Diseases. 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.

What is Leishmaniasis
ie. kala-azar

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 sand flies.

The most common forms of leishmaniasis 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.

Cause of Leishmaniasis ie. kala-azar

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.

Authors of the study are affiliated with Universidade Federal de São Carlos, São Carlos, Brazil (S.R. Maruyama, N.T. Takamiya, T.Y. Takahashi, L.A. Rogerio, C.A.B. Oliveira); Universidade Federal de Sergipe, Aracaju, Brazil (A.K.M. de Santana, A.R. Jesus, A.S. Barreto, A.M. da Silva, R.P. Almeida); Universidade de São Paulo, Ribeirão Preto, Brazil (C.M. Milanezi, V.A. Trombela, A.K. Cruz); National Institutes of Health, Rockville, Maryland, USA (J.M. Ribeiro); Fundação Oswaldo Cruz Bi-institucional, Ribeirão Preto, Brazil (J.S. Silva).

Main author of the study Dr. Maruyama is an early-career investigator based in the Department of Genetics and Evolution at Federal University of São Carlos, Brazil, as Research Fellow through the FAPESP Young Investigator Award agreement. Her primary research interests include understanding parasite–host interactions through comparative genomics and functional genomics. Dr. Santana is a postdoctoral fellow in the Department of Biochemistry and Immunology, Ribeirão Preto Medical School, University of São Paulo, Brazil. Her primary research interest is in innate immunity and regulation of the immune response by intracellular pathogens.

Emerging parasitic disease mimics the symptoms of visceral leishmaniasis (kala-azar) in people

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