Visceral Infections: Protozoa

Snapshot

A 50-year-old healthcare worker presents to the emergency room after a month-long trip to India. He reports having fevers, abdominal pain, and a 5-lb weight loss over the past week. He recalls being bit by multiple types of bugs during his summer month in India. His past medical history includes gonorrheal urethritis. His social history includes having several different male sexual partners over the past year often without protection. On physical exam, there is hepatosplenomegaly. He is treated for a presumed parasitic infection, given his clinical risk factors, and tested for HIV. (Visceral leishmaniasis)

Introduction

Protozoa
- single-celled eukaryotes, often parasitic, that feed on organic tissues

Infections of Protozoa
Central Nervous System	Gastrointestinal	Visceral Infections	Hematologic Infections	Sexually Transmitted Diseases
Toxoplasma gondiiNaegleria fowleriTrypanosoma bruceiAcanthamoeba	Giardia lambliaEntamoeba histolyticaCryptosporidium	Trypanosoma cruziLeishmania donovani	Plasmodium Babesia	Trichomonas vaginalis

Trypanosoma cruzi

Introduction
- clinical syndrome
  - Chagas disease
- transmission
  - via triatomine, a type of reduviid bug (“kissing bug”)
    - painless bite that deposits feces
- demographics
  - South America
- risk factors
  - poor sanitation
  - tropical areas
  - immunosuppression
Presentation
- acute infection
  - Romaña sign is a characteristic sign
    - unilateral periorbital swelling
  - chagoma on the skin at the site of inoculation
- chronic infection
  - dilated cardiomyopathy
    - apical atrophy
  - megacolon
  - megaesophagus
Imaging
- chest radiograph
  - cardiomegaly
- barium swallow or barium enema
  - dilated esophagus
  - dilated megacolon
Studies
- peripheral blood smear
  - trypomastigotes (motile flagellated form)
- detection of antibodies via serology
- detection of DNA via polymerase chain reaction (PCR)
Treatment
- benznidazole or nifurtimox
  - first-line

Leishmania donovani

Introduction
- clinical syndrome
  - visceral leishmaniasis (also known as kala-azar or black fever)
  - cutaneous leishmaniasis
- transmission
  - via sandfly bites
- demographics
  - younger children
  - mostly found in India, Bangladesh, Sudan, Ethiopia, and Brazil
- risk factors
  - HIV/AIDS
- prognosis
  - visceral leishmaniasis is fatal without treatment
Presentation
- visceral leishmaniasis (kala-azar)
  - spiking fevers
  - weight loss
  - hepatosplenomegaly
  - abdominal pain
- cutaneous leishmaniasis
  - skin papules that progress to nodule or ulcer
Studies
- pancytopenia
- biopsy or needle aspiration of bone marrow or skin lesions
  - macrophages with ingested amastigotes (flagella-lacking form)
- urine antigen testing
Treatment
- amphotericin B or sodium stibogluconate
  - first-line
- miltefosine
  - second-line
Complications
- post-kala-azar dermal leishmaniasis
  - chronic skin rash with onset months to years after treatment
  - erythematous or hypopigmented polymorphic lesions throughout the body