Westchester Community College 9

Cryptosporidium Overview

  • Definition: A parasitic organism that can infect almost any mammal

  • Distinction: Do not confuse with Cryptococcus neoformans, a fungal disease affecting only immunocompromised individuals.

Characteristics of Cryptosporidium

  • Lacks Definitive Host:

    • No known definitive host; controversy about its evolution regarding host requirements.

    • Hypothesis suggests it may have evolved from a lineage that had a definitive host that is now extinct.

  • Transmission:

    • Can be spread through contaminated water (e.g., public pools) after infected mammals, including raccoons or even children, contaminate the water supply.

    • The cyst form of Cryptosporidium is resistant to chlorine, making chlorination ineffective in killing it.

Public Health Impact

  • Outbreaks: Known for causing widespread outbreaks in communities. Outbreaks can make up to 50% of the population sick in small towns.

    • Example: FDR Park reported at least five outbreaks in the last decade.

  • Symptoms: Generally self-limiting but causes severe diarrhea, which can overwhelm healthcare resources.

  • Long-Term Effects: Outbreaks often lead to stress on local health care facilities due to sudden influxes of patients.

Plasmodium Overview

  • Definition: The genus of parasites responsible for malaria.

  • Distribution:

    • Present on five continents (excluding Australia and Antarctica).

  • Key Species:

    • Plasmodium falciparum: Most severe form, prevalent in Northern Africa and Southern Europe.

    • Plasmodium vivax: Common in Southeast Asia and also the Americas.

    • Plasmodium malariae and ovale: Found primarily in North and South America.

Transmission and Life Cycle of Plasmodium

  • Vector: Spread by the Anopheles mosquito, which serves as the definitive host.

  • Intermediate Hosts: Humans and other mammals, except chickens.

  • Life Cycle Stages:

    1. Mosquito Infection: Anopheles mosquito injects saliva (anesthetic) into the host while transmitting Plasmodium.

    2. Liver Phase (Exoerythrocytic Cycle):

      • Initial infection of liver cells (hepatocytes).

      • Different species exhibit different behaviors: e.g.,

        • Falciparum: Short-lived in the liver.

        • Vivax: Can remain dormant for years.

    3. Schizogony: Rapid division in hepatocytes produces numerous new Plasmodium cells.

    4. Blood Phase (Erythrocytic Cycle):

      • Infected liver cells release Plasmodium into the bloodstream to infect red blood cells.

      • Identification can occur via microscopy.

Symptoms and Effects of Malaria

  • Paroxysms: Defined as cyclic worsening symptoms due to repeated rupturing and infection of red blood cells.

  • Symptomatic Phases:

    1. Cold Phase: Due to lack of oxygen delivered to body, resulting in chills.

    2. Hot Phase: Immune response to rupture of red blood cells, causing fever and malaise.

    3. Wet Phase: Overexertion of the immune system causes extensive sweating and fatigue.

  • Asymptomatic Phase: Varies by species, Falciparum averages a 3-day cycle, while others can extend to months.

Final Notes

  • Overall Impact: Without treatment, malaria can lead to increasing severity of symptoms, resulting potentially in death due to a lack of red blood cells.

  • Focus for Study: Understand paroxysms, the life cycle of Plasmodium, and key differences among the species affecting human infection. Emphasize understanding the mechanisms of symptom development related to schizogony and the overall impact on healthcare systems.