Tropical Diseases in Ghana: Units VII and VII

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Tropical Diseases in Ghana Units VII and VII

• Malaria

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Epidemiology of Africa

• A slide series from WHO is available online. It
  provides an overview of the entire continent of
  Africa in epidemiological blocks.
• Go to http//whoafr.org/ddc/presentations/trends_
  of_epidemic_prone_diseases_files/frames.htm
• Notethe abbreviation CSM is usedI am fairly
  certain it stands for chloroquine sensitive
  malaria.

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Ghana

• For Ghana, the diseases we will review are the
  following malaria, yellow fever and other viral
  hemorrhagic fevers (VHF) meningococcal
  meningitis, cholera, polio,hepatitis

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Malaria

• between 2 - 3 million people die of malaria each
  year, the great majority of them in Africa
• For information on malaria in West Africa, go to
  the CDC page
• http//www.cdc.gov/travel/wafrica.htm
• This page will also give you current info about
  outbreaks of various diseases in Africa

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Definition

• Malaria is an acute and chronic diseasecaused by
  an obligate intracellular parasitethe most
  common being Plasmodium falciparum
• Transmitted to humans by bite of female
  ANOPHELES MOSQUITOES

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Life Cycle

• The organism undergoes 1 sexual reproduction
  cycle in mosquito, and 2 asexual cycles in
  humansone in liver and the other in RBCs
• Infected mosquito bites human. Saliva contains
  sporozoites which are injected into capillaries
  these stay in blood for only about 30 minutes

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Life Cycle

• Exoerythrocytic Phase
• Phagocytic cells attempt to destroy sporozoites,
  but remaining organisms enter liver parenchymal
  cells.
• Here they multiply asexually in
  shizogony/merogony
• Hepatocytes fill with organisms and eventually
  rupture (6-16 days) Merozoites enter circulating
  RBCs

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The organism

• The following pages show electron micrographs of
  the four principal stages in the asexual cycle of
  Plasmodium falciparum the merozoite, the ring
  stage, the trophozoite and the schizont

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Stages

• Mid-trophozoite stage, showing the nucleus, the
  pigment vacuole and a cytostome with a forming
  food vacuole. "Trophozoite" means the maturing
  stage. Greek "tropho" means "to nurture".

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stages

• A ring stage of the cup-like form, showing the
  nucleus surrounded by ribosomes and some
  endoplasmic reticulum. The species name
  falciparum means "crescent-shaped" and refers to
  the appearance of the ring stage.

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Stages

• A merozoite, showing the apical prominence with a
  rhoptry, dense granules, and a very indented
  nucleus

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stages

• A schizont, showing a series of nuclei and
  developing merozoites containing rounded early
  rhoptries around their perimeters. A lipid
  vacuole is present centrally. Note the irregular
  appearance of the RBC surface and the presence of
  knobs. The name "schizont" comes from the Greek
  "schizo", meaning "to tear apart".

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Epidemiology

• Level of transmission determined by
• Seasonal incidence and prevalence within the
  reservoir host (human)
• Characteristics of the local vector mosquitoes
• Susceptibility of the local human population
• Local climatic and environmental features

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The Host

• Immunity populations in endemic areas develop
  some degree of immunity
• Children, who have the least acquired immunity,
  are most susceptible
• Asymptomatic individuals may serve as a reservoir

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The Host

• Heterozygotes for sickle cell anemia are
  resistant less severe infection
• Famines can blunt malaria epidemics
• Malnutrition may also antagonize growth of the
  parasites

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The Vector

• Vector effectiveness depends upon sufficient
  numbers and its preference for human rather than
  animal blood
• How long mosquito lives also important and this
  is influenced by climate
• 37 different species of anopheles mosquitoes

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The Environment

• Malaria transmission profoundly influenced by
  climate
• High humidity (at least 60)
• Temperature between 20-30 degrees centigrade
• Rainy season promotes breeding but heavy rains
  can wash out breeding sites

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Stable endemic malaria

• This is what we see in Ghanaa fairly predictable
  incidence and prevalence of illness

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Pathophysiology of malaria

• Erythrocytes are destroyed when parasitized cells
  rupture and severe anemia can develop Renal
  failure can be caused by aggregated hemoglobin in
  tubules
• Infected persons have high levels of circulating
  TNF. TNF may cause symptoms.

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Pathophysiology

• Hypoglycemia common due to parasite consumption
  of glucose and decreased liver gluconeogenesis
• Metabolic acidosis and hyponatremia
• Small Intestine malabsorption
• ARDS
• Renal abnormalities
• Neurological (brain is heavily parasitized in
  severe infections)

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Clinical Manifestations

• Prodromal Sx 2-3 days before acute phase,
  characterized by malaise, anorexia, fever
• Paroxysm lasts 9-10 hours. Typical onset is
  shaking chills followed by fever (104-106
  degrees) within 30-60 minutes, with diaphoresis,
  headache, malaise, fatigue and myalgia
• hot stage lasts 2-6 hours
• Sweating stage in which temperature drops lasts
  2-3 hours
• Periodicity Schizonts mature and rupture every
  48 hours

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Physical Assessment

• Tachycardia
• Fever
• Enlarged spleen
• Hepatomegaly with tenderness
• Orthostatic hypotension
• Mental confusions, jaundice, tachypnea
• Recurrent H.simplex

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Diagnosis

• Gold Standard is blood smears
• Dipstick technique available
• Fluorescent staining of parasites in blood sample

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Treatment

• Choice of drugs and drug regimes vary with the
  species of Plasmodium, economics, and drug
  sensitivities
• Prophylactic drugs act on liver development of
  malarial parasites

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Antimalarial drugs currently in use

• Artemisine, artemether, and artesunate
• Atovaquone
• Chloroquine and amodiaquine
• Halofantrine
• Mefloquine
• Primaquine
• Proguanil
• Pyrimethamine
• Quinine, quinidine
• Sulfadoxine
• Tetracycline