Malaria Parasites and Epidemiology

• Malaria is a serious, sometimes fatal disease caused by a parasite
• The parasite infects a certain type of mosquito, which feeds on human blood
• Those who get malaria typically experience high fevers, shaking chills and flu-like illness

Malaria Parasites

• Malaria parasites are microorganisms of the genus Plasmodium
• There are over 100 species of Plasmodium that can infect various animal species
• Four Plasmodium species that infect humans include:
  • P. falciparum
  • P. vivax
  • P. ovale
  • P. malariae
• The Anopheles mosquito is a vector

Epidemiology

• In 2016, malaria cases were at 198 million worldwide
• 500,000 people died in 2016
• Most deaths were children in the African region
• Plasmodium falciparum is the most common, accounting for over 90% of the global malaria burden
• Nigeria reports the most malaria cases and deaths in the world
• Climate is a key determinant in the geographic distribution and seasonality of malaria

Status in Sudan

• Sudan has a high burden of malaria-related morbidity and mortality
• A national malaria control programme supported by the WHO reduced malaria cases from over four million in 2000 to less than one million in 2010
• Malaria deaths in Sudan decreased by 75% between 2001 and 2010
• 75% of the population in Sudan and South Sudan is at risk of malaria
• Far North regions have no malaria transmission, while the North, East and West are seasonal

Malaria Vector

• The female Anopheles mosquito is a vector of malaria
• Anopheles arabiensis and Anopheles gambiae are types of female Anopheles mosquito responsible for malaria transmission.
• Female Anopheles mosquitoes suck blood for ova production

People at Risk

• Groups most at risk from malaria:
  • Young children and infants
  • Travelers from areas with no malaria
  • Pregnant women and their unborn children
• Poverty, lack of knowledge and lack of access to healthcare contribute to malaria deaths worldwide

Routes of Transmission

• Malaria is spread from:
  • Bites of female anopheles;
  • Trans-placentally;
  • Intravenously, through blood transfusion
• Reservoir: Humans

Incubation and Communicability

• Incubation period: between 7 to 30 days
• Shorter incubation periods are frequently seen with P. falciparum
• Longer incubation periods are seen with P. malariae
• Untreated or inadequately treated infected cases may remain infectious for years as gametocytes persist
• Infected mosquitos remain infected for life

Case Classification

Suspected Case:

• Detection of Plasmodium species by rapid diagnostic antigen testing without confirming with microscopy or nucleic acid testing in any person, regardless of previous malaria episodes outside the country

Confirmed Case:

• Detection and specific identification of malaria parasites by microscopy on blood films OR by a nucleic acid test in a laboratory with appropriate expertise in any person

Life Cycle of Plasmodia

• Plasmodia has two types of life cycle:
  • Schizogony (asexual cycle) in humans;
  • Sporogony (sexual cycle) in female anopheles mosquito

Schizogony (Asexual cycle)

• Sporozoite, injected into human blood during mosquito bites, is the infective stage
• Sporozoites circulate in blood for about 30 minutes, and invades a hepatocyte
• Growth and multiplication timing depends on the Plasmodia species

P. vivax and P. ovale

• Some sporozoites can remain dormant in the hepatocytes for a week, month or even years before their growth and division
• After the dormant period, sporozoites are reactivated, producing merozoites
• Hypnozoites are responsible for long incubation and late relapses
• (Cause of relapse)

RBC Infection

• Exo-erythrocytic merizotes invade RBCs
• Plasmodium falciparum merozoite infects RBC of any age
• Plasmodium vivax and Plasmodium ovale infect young RBCs
• Plasmodium malariae infects infects only old RBCs

Gametocytes

• Some trophozoites develop into sexual stages called gametocytes (macrogamete=female, microgamete=male) instead of schizonts
• Sexual stages undergo sporogony (sexual cycle) if a female anopheles mosquito bites such a person

Sporogony (Sexual cycle)

• The female mosquito sucks sexual states in blood
• Microgamate flagellum fertilizes a macrogamate creating a zygote
• Zygote develops into ookinete, that develops into an oocyst containing many sporozoites
• Oocyst ruptures releasing sporozoites that move to the salivary glands
• Mosquito becomes infective by the final stage

Clinical Picture

• Clinical signs of Malaria include:
  • Fever
  • Headache
  • Nausea
  • Vomiting
  • Sweating
  • Back pain
  • Anemia
  • Splenomegaly
  • Chills
  • Hepatomegaly
  • Fatigue
  • Muscular fatigue

Uncomplicated Malaria

• A patient with fever, or a history of fever within the 48 hours (with of without other past symptoms like nausea, diarrhoea, vomiting, headache, chills, myalgia)

Severe Malaria

• Defined as malaria due to P. falciparum, which becomes immediate threat to life, a medical emergency requiring hospitalization
• Severe malaria occurs when infections are complicated by organ failures or abnormalities in a patient's blood or metabolism

Severe symptoms

• A patient with symptoms of uncomplicated malaria, plus drowsiness with extreme weakness
• Associated signs and symptoms related to organ failure (e.g. disorientation, loss of consciousness, convulsions, severe anaemia, jaundice, haemoglobinuria, spontaneous bleeding, pulmonary oedema and shock)

Complications of Malaria

• Hyperpyrexia
• Hypoglycemia
• Lactic Acidosis
• Dehydration
• Cerebral Malariae
• Renal Failure
• Black water fever
• Pulmonary edema

Diagnosis of Malaria

• Should be suspected clinically
• Thick and thin blood films are used in diagnosis
  • Thick film: are 20x more sensitive than thin smears, but speciation may difficult
  • It is good for fast detection of the parasite
  • Thin films: essential to confirm diagnosis and identify species
• Other tests include:
  • CBC: low Hb, low platelets
  • Hypoglycemia tests rule out cerebral malaria
  • Urea and creatinine tests
  • Bone marrow examination when the parasite has not been found in the blood film
  • ELISA is complementary
  • Rapid diagnostic test (RDT)
• According to IMCI, manage any child with a temperature over 37.50C or feeling hot as malaria, after ruling out obvious causes of fever (tonsillitis, measles, abscess, UTI, Acute respiratory infection)

Treatment

• Artemisinin-based combination therapies (ACT) are the treatments recommended for uncomplicated falciparum malaria including:
  • infants
  • people living with HIV/AIDS
  • home-based management cases
  • Pregnant women in the 2nd and 3rd trimesters
• Exception: 1st trimester of pregnancy
• First line treatment includes:
  • Coartem tabs
• Second line treatment includes:
  • Artesunate injection
• Third line treatment includes:
  • Quinine dihydrochloride, quinine hydrochloride, quinine sulphate
  • An oral quinine dose of 10 mg salt\kg 8 hourly for 7 days
  • Injectable Quinine given intramuscularly

Prevention and Control

• In Sudan, the population are all at risk but the following special groups are at a higher risk:
  • Travellers from malaria free areas
  • Pregnant women
  • splenectomized individuals.

Prevention

• Prevention is acheived through vector control
• Aims to reduce contacts between mosquitoes and humans
• Some vector control measures involve:
  • Destruction of larval breeding sites
  • Insecticide spraying inside houses requiring organized teams
• Personal protection measures include:
  • Insecticide-treated bed nets
  • Case management diagnosis and treatment to patients
• Health education
• Training and supervision of health workers, to ensure that they carry out their tasks correctly

Malaria Control

• Goal is to reduce the health impact of malaria on the population, as much as possible in malaria-endemic countries
• The main components of the National strategic Plan for malaria includes:
  • Ensuring early diagnosis and prompt treatment
  • Multiple preventions such as vector control, insecticide nets and intermittent preventive treatment for pregnant mothers
  • Forecasting, early detection and containment of the epidemics
  • Strengthening of the malaria control activity through improvement of the information system and implementation of operational research results

Roll Back Malaria Program

• The overall aims of RBM is to reduce the burden of malaria by reducing malaria morbidity and mortality.
• Effective management of malaria
• Rapid diagnosis and treatment
• Multiple prevention
• Focused research
• Well coordinated action
• Dynamic global movement