parasitology (apicomplexa)

PARASITOLOGY

(apicomplexa)

Apicomplexa ( Sporozoa)-all apicomplexans are obligate intracellular parasites and have an apical complex. -elongated shape 

APICAL COMPLEXmicronemesRhoptriesPolar rings

-apicomplexans replicate via schizogony.

3 Distinct processes of Apicomplexan Life Cycle

Sporogony-asexual reproductive phase

Gamogony/gametogony-sexual phase

Female gametes + Male gametes = ookinete/sporoblast

Merogony-asexual reproduction; cellular products are called merozoites.

Diseases cause by Apicomplexan Organism

•Babesiosis•Malaria•Forms of cocciodiosis including -Cryptosporidiosis -Cyclosporiasis -Isosporiasis -Toxoplasmosis

CRYPTOSPORIDIUM PARVUM

•Cryptosporidium parvum is a protozoan and an obligate intracellular parasite (a parasite that cannot survive without a host) that commonly causes an opportunistic infection in immunocompromised hosts.

•C. parvum is considered to be the most important waterborne pathogen in developed countries.

Disease cause by C.parvum

• Cryptosporidiosis (krip-to-spo-rid-e-O-sis), is a diarrheal disease caused by microscopic parasites, Cryptosporidium, that can live in the intestine of humans and animals and is passed in the stool of an infected person or animal. Both the disease and the parasite are commonly known as "Crypto"..

Morphology

Oocysts• Size: 4-6 μm.• Morphology: round,

oval• They are mainly

located in the jejunum.

Life cyle

•Crypto begins its life cycle as sporulated oocysts (1) which enter the environment through the feces of the infected host.

•The infective oocysts reside in food and water (2).

•Infection occurs when the oocysts are ingested by a suitable host (3)

Life Cycle

Swallowing pool water that has been contaminated with the parasite

In contaminated food or drink (called heteroinfection).

By faeco-oral route (hand to mouth) in already infected patient ( called external autoinfection).

by touching your mouth after touching the stool of infected persons or animals or touching soil or objects contaminated with stool.

Mode of transmission

•Increased intestinal secretion of sodium and chloride, water absorption is inhibited

•Epithelial cells damaged by:

•Parasite invasion and multiplication

•May produce up to 10-20 liters of watery stools per day

Pathogenesis

•The first signs and symptoms of cryptosporidium infection usually appear within a week after infection and may include:

•Watery diarrhea•Dehydration•Lack of appetite•Weight loss

Symptoms

•Stomach cramps or pain•Fever•Nausea•Vomiting•Symptoms may last for up to: 1-14 days, though they may come and go sporadically for up to a month, even in people with healthy immune systems. Some people with cryptosporidium infection may have no symptoms

TREATMENT

• paromomycin, may reduce the symptoms of crypto

• drink plenty of fluids.

• Nitazoxanide has been FDA-approved for treatment of diarrhea caused by Cryptosporidium

Treatment

HIV-positive individuals who suspect they have cryptosporidiosis should contact their health care provider. For those persons with AIDS, anti-retroviral therapy that improves the immune status will also decrease or eliminate symptoms of cryptosporidiosis. However, even if symptoms disappear, cryptosporidiosis is often not curable and the symptoms may return if the immune status worsens.

Prevention

1. The easiest way to prevent cryptosporidiosis is to practice good hygiene, especially after using the toilet.. b. After handling animals

2. After touching dirt3. Before preparing food4. Avoid drinking untreated water5. Peel and rinse fruits and vegetables6.Follow water advisories7.Boiling and microfiltration of drinking water

CYLOSPORA CAYETONENSIS

General Characteristics

•is an apicomplexan, cyst-forming coccidian protozoan that causes a self-limiting diarrhea

•unicellular parasite that causes an intestinal infection called cyclosporiasis.

• Acid-fast variable, have been found in the feces of immunocompetent travellers.

•Pathogenic

Morphology

• has sphericaloocysts that are between 7.5 and 10 micrometers in diameter.

• a 50-nanometer-thick wall with an outer threadlike coat called a wrinkle

• By drinking water or eating food that's been contaminated by an infected person.

• type of sanitation and contact with soil

• direct person to person transmission

• through the fecal-oral 

• visiting regions where the species is endemic.

Mode of Transmission:

Life Cycle

Sign and Symptoms

•Nausea•Vomiting•Muscle aches•Low-grade fever•Fatigue•General feeling of unwellness •Burping•Stomach cramps

• Watery diarrhea

• Frequent and sometimes explosive bowel movements

• Bouts of diarrhea alternating with bouts of constipation

• Loss of appetite

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Prevention

•  The simplest one is to warn travelers not to visit regions where the protozoan is endemic.

• Individuals in endemic areas should wear gloves when gardening to prevent exposure to oocysts.

• Thorough washing may help remove oocysts.

Therapy

• Patients have been treated symptomically with antidiarrheal preparations and have obtained some relief;

• Trimethoprin(TMP-SMX)

• orally twice daily for seven days.

Elimination of parasites a decrease in diarrhea.

diminished abdominal pain occur within 2-3 days after treatment.

• Patients with AIDS needs higher dose and long term

Sarcocystis spp.

Sarcocystis spp.General Characteristics:

-Two well described Sarcocystis spp. include S. bovihominis(cattle) and S. suihominis (pig). When uncooked meat from this infected animals ingested by humans, gamogony(fission resulting in the production sporozoan gametes) can occur in the intestinal cells, with eventual production sporocysts in stool.

-Sarcocystis spp. Have an obligatory 2 hosts life cycle.•Intermediate host(herbivores and omnivores)- infected through ingestion of sporocysts secrete in the feces of the definitive host.•Definitive host (carnivores and omnivores)-Human who have ingested meat containing the mature sarcocysts serve as the definitive host.

For immunocompromised hosts:

-fever-sever diarrhea-abdominal pain-weight loss. -Sporocysts found in the stool are broadly oval and slightly tapered at the ends. - 9-16 um long

Pathogenesis and Spectrum of Disease-when human ingests oocysts from other animal stool sources, the sarcocysts that develop in human muscle are 7-16 um long and cause few problems. Basically, no inflammatory response, no evidence of pathogenicity is seen.

CORTICOSTEROIDs- reduce allergic inflammatory reactions.

Ingestion of Infected meat manifests primarily intestinal disease within few hours after consumption, characterized by;NauseaAbdominal painDiarrhea

However, patients may be asymptomatic.

Prevention

•Cooking meat to an internal temperature higher than 67degree kills taxoplasma gondii tissue cysts in meat.

•Preventing cattle, buffalos, and swine from consuming human feces shedding infective oocysts also prevents animal infection.

•When human are intermediate hosts, preventive measures involve careful disposal of animal feces that may contain the infective sporocysts.

Treatment

•no known treatment or prophylaxis is available for intestinal infection, myositis, vasculitis, or related lesions caused by human sarcocystosis.

•Supportive therapy for patients with severe diarrhea is indicated.

MICROSPORIDIA

MiCROSPORIDIA

• = intracellular spore - forming parasites;=clinical manifestations of microsporidiosis include intestinal, pulmonary, ocular, muscular, and renal disease. Microsporidiosis has been identified in immunosuppressed hosts ,travelers, children, and the elderly.

=shared the same features with fungi

Morphology

-spores are all round and oblong, and those associated with human infection tend to be about 1-4 um size.

THE LIFE CYCLE

Transmission:

• human-to-human

• animal-to-human

• water transmission

• inhalation or ingestion

DIAGNOSTIC TESTS

FecalysisUrinalysisOther body fluid or tissues

Transmission electron microscopy-gold standard for identifying specific spp.

PREVENTION

•NO vaccine available

•Filtrating water supply

•Taking precaution when handling body fluids

•Improving personal hygiene(e.g handwashing)

THERAPY,TREATMENT

Albendazole- Gastro, muscle, disseminated and ocular infections.Metronidazole- E. bieneusi and others.Fumagillin- Keratoconjunctivitis and ocular lesions (Encephalitozoon spp. B. algarae, E. hellum, E. cuniculi, V. corneae); Not approved by FDA for microsporidiosis.