Microbiology Chapter 12

RBCs bursts, releasing merozoites, which reinvade RBC. This event leads to......

the "attack" symptoms *number of merozoites, timing, depends on sp.

Sir Ronald Ross and the History of Malaria

Sir Ronald Ross discovered the cause of Malaria. Plasmodium in the Anopheles mosquito

notes: effects of Malaria on spleen

enlarged spleen

The Eukaryotes: Parasites Emphasizing Malaria and Cryptosporidium

**Malaria kills one child every 30 seconds

Why the concern?

**most prevalent disease in the world -3.5 billion live in MALARIOUS areas -100-300 + million new cases annually -1-3 million deaths annually (ave.=2 mil.) - >300 million cases, total (cum.) - serious threat to children

What causes Malaria?- ancient disease

-Five species of Plasmodium -P. falciparum (malig.) -P. vivax (benign) -P. ovale -P. malariae -P. knowlesi (new) -Disease can be: -Acute (sudden onset) -Chronic (long term)

What is Malaria

-Mal aria means "Bad air" itian) - from swamps - this concept lasted about 2500 years -a mosquito-borne parasitic disease -transmitted only by Anopheles Mosquitoes -it is caused by a protozoan which grows and develops in the erythrocytes of its host; identified by a signet ring -protozoan parasites of the genus

Malaria Summary

-Mosquito bite transmits sporozoite into bloodstream -enters the liver cells (which undergo schizogony), resulting in the release of merozoites into the bloodstream -Merozoites infect RBCs and again undergo schizogony -ruptures the infected RBCs, releasing toxic compounds -causes paroxysms of chills and fever -some merozoites develop into gametocytes and are taken up by a mosquito, repeating the cycle

Cryptosporidium- Apicomplexa

-Nonmotile; obligate intracellular parasites -complex life cycles like Plasmodium -Cryptosporidium- transmitted via feces; waterborne illness; watery diarrhea -causes #1 recreational parasitic waterborne illness

Malaria Notes

-Plasmodium vivax is a 'mild' type of malaria. It sometimes called benign malaria, similar to having the 'flu.' -it can be serious for children, its affect migh tbe like Plasmodium flaciparum, severe malaria. It frequently kills children. it is dangerous. this one is associated with Sickle-cell trait

Vocab terms

-Schizogony is form of division in which a series of nuclear divisions takes place before the segmentation of the cytoplasm (product is usually merosoites in man) -Sporogony production of sporozoites by repeated divisions of a zygote. Schizogony in which the product is sporozoites (in mosquito) -Paroxysms: a sudden recurrence or "attack" of a disease. These include 3 stages- cold, hot, and sweating (major symptoms)

ACUTE symptoms (sudden onset)

-classical cyclic paroxysm (RBCs burst): "the attack" symptoms -cold stage: chills and shaking -hot stage: warm, headache, vomiting -sweating stage: weakness -feel well for period of time, then cycle repeats itself

Anopheles sp.

-eggs are laid on water -most breed in stagnant mangrove swamps, sunny pool, edges of trickling streams -feed with body slanted away from host -very important vectors of human Malaria -primary vectors in U.S. were -A. quadrimaculatus -A. freeborni

Summary

-mosquito borne infectious disease -tropics, subtropics -P. falciparum, vivax, ovale, malariae, knowlesi -incubation period nearly two weeks -cyclic paroxysms (alternating chills & fever) -fever -thick and thin blood smears for diagnosis -treatment is by "antibiotics" (antimicrobials) and varies by geography

modern trends

-prophylaxis: quinine water -chloroquine: drug of choice -malarone: atovaquone and proguanil -mefloquine (side effect- hallucination) -treatment (combination therapy) -artemisinin: artesunate and artemether -control -bed nets

environmental factors

-temp: below 86 F, above 68F -rainfall: thrive in tropical areas -altitude: rarely exist above 2000 meters -terrain: coastal areas and lowlands with lots of freshwater breeding sites

Definitions for Malaria Life Cycle

1- Trophozoite: active feeding form (ring stage) 2-Sporozoite: (in mosquito) daughter cell resulting from sporogony 3-Merozoite: (in man) a daughter cell resulting from schizogony 4-Gametocytes: cells that take place in sexual reproduction (in mosquito) **disease of RBC NOT WBC

Life cycle of Plasmodium vivax, the apicomplexan that causes Malaira

Asexual (intermediate host) 1-infected mosquito bites human; sporozoites migrate through bloodstream to liver of human 2-sporozoites undergo schizogony in liver cell; trophozoites called merozoites are produced 3-merozoites released into bloodstream from liver may infect new red blood cells 4-merozoite develops into ring stage in RBC 5-ring stage grows and divides, producing merozoites 6-merozoites are released when RBC ruptures. Some merozoites infect new RBCs, and some develop into male and female gametocytes Sexual (definitive host) 7-Another mosquito bites infected human and ingests gametocyte 8-in mosquitos digestive tract, gametocytes unite to form zygote 9-resulting sporozoites migrate to salivary glands of mosquito

Life cycle of Plasmodium protozoa

Asexual cycle (in humans) 1- Preerythrocytic Phase (10 days) (prior to RBCs) -sporozoites -merozoites (liver) 2- Erythrocytic Phase (2 days) (in RBCs & symptoms) -merozoites -schizogony -trophozoites -schizonts -merozoites 3- Differentiation into specialized sexual forms -macrogametocytes -microgametocytes

Rapid Diagnostic Test (RDT) for Malaria

Malaria RDTs, sometimes called "dipsticks assist in the diagnosis of malaria by providing evidence of the presence of malaria parasites in human blood. RDTs are an alternative to diagnosis based on clinical microscopy -tests for 3 species in West Africa -99% diagnostic and 99% sensitive

most major complications of malaria due to clogged capillaries

in spleen in liver in kidney in the brain -attaches to endothelium of capillary wall: tissue death

Traditional Treatments

Oldest Chinese- Artesminin Herb -now newly modified for modern use Chloroquine in most areas -Quinine and Doxycycline OR -Mefloquine -Primaquine- best for hypnozoites in relapse -also sulfa drugs and antibiotics used

Virus properties and change

Properties: small size, specificity, -RNA or DNA (not both); SS, DS Change: 1-antigenic variation= rhinovirus 2-antigenic drift= 'flu'- seasonal 3-antigenic shift= 'flu'- pandemic

Life cycle of Plasmodium protozoa (continued...)

Sexual cycle (in mosquito) 1-macrogametocyte and microgametocyte 2-zygote (diploid) 3-oocyst 4-sporozoites (haploid)

Malaria Notes

The life cycle involves two phases and two hosts: -the sexual phase occurs in the female anopheles mosquito, which requires blood meals for egg development -the asexual phase occurs in humans Sporozoites are the infective stage that's found in the mosquito; Sporozoites are injected into a human by the female Anopheles mosquito during a blood meal The sporozoites travel to the liver where most develop into tissue schizonts that are filled with merozoites. After 1-2 weeks the liver cells containing the schizonts burst and merozoites are released into the bloodstream where they invade and infect RBCs. With vivax ovale infections, some sporozoites will develop into hypnozoites, lying dormant in the liver. These hypnozoites will become active at some later time, complete the rest of their life cycle, causing symptomatic malaria (known as "relapse") Merozoites then invade the RBC and become trophozoites The trophozoites develop into blood schizonts that contain more merozoites. When the RBC ruptures, these merozoites will invade more RBCs, causing a cascade effect with more and more RBCs becoming infected, thus causing the signs and symptoms of Malaria TO REVIEW: -the malaria parasitic life cycle involves sexual (mosquito) and asexual (human) phases -Anopheles mosquito (female) is the primary host -the liver stage infection is asymptomatic and involves sporozoites, tissue merozoites and schizonts, and in case of vivax ovale, hypnozoites -the RBC stage is symptomatic and results from the cascade effect of rupturing RBCs, and involves the trophozoites, erythrocytic merozoites, and schizonts.6

-Understanding the life cycle of the malaria parasite is most important that you're familiar with the overall biology. This helps you understand how chemoprophylaxis and treatment of malaria work.

The life cycle involves two phases and two hosts: -The sexual phase occurs in the female Anopheles mosquito, which requires blood meals for egg development. -The asexual phase occurs in humans. -Sporozoites are the infective stage that's found in the mosquito. Sporozoites are injected into a human by the female Anopheles mosquito during a blood meal. -The sporozoites travel to the liver where most develop into tissue schizonts that are filled with merozoites. After 1-2 weeks the liver cells containing the schizonts burst and merozoites are released into the bloodstream where they invade and infect RBCS. With vivax and ovale infections, some sporozoites will develop into hypnozoites, lying dormant in the liver. These hypnozoites will become active at some later time, complete the rest of their life cycle, causing symptomatic malaria ( known as a "relapse"). -Merozoites then invade the RBC and become trophozoites -The trophozoites develop into blood schizonts that contain more merozoites. When the RBC ruptures, these merozoites will invade more RBCs, causing a cascade effect with more and more RBCs becoming infected, thus causing the signs and symptoms of malaria. To review: -The malaria parasitic life cycle involves sexual (mosquito) and asexual (human) phases. -Anopheles mosquito is the primary host. -The liver stage infection is asymptomatic and involves sporozoites, tissue merozoites and schizonts, and in the case of vivax and ovale, hypnozoites. -The RBC stage is symptomatic and results from the cascade effect of rupturing RBCs, and involves the trophozoites, erythrocytic merozoites and schizonts.

blood smear- best diagnosis

but now less common due to costs; RDT (rapid diagnostic test) *problem: P. falciparum "disappears" from blood

malaria and "sickling" in RBCs

mutation of one DNA base results in sickle cell anemia! *sickle cell hemoglobins stick together

Mosquito types compared "most dangerous animal on earth"- Bill Gates

types: Culex pipiens, Aedes aegypti, Anopheles gambiae *mosquito vector complex -Diseases, but also mosquitos, are good in that they pollinate plants -West Nile Encephalitis, Zika Virus, Yellow Fever, Malaria