Tropical disease in the child: Malaria, Typhoid, Dengue Flashcards
Define malaria.
Malaria is a mosquito-borne infectious disease affecting humans and other animals caused by parasitic protozoans (a group of single-celled microorganisms) belonging to the Plasmodium type.
Explain the aetiology/risk factors of malaria.
Malaria is caused by Plasmodium species, which are protozoal blood parasites. The following 4 species can infect humans:
- P vivax
- P falciparum
- P malariae
- P ovlae
The bite of an infected mosquito introduces asexual forms of the parasite, called sporozoites, into the bloodstream. Sporozoites enter the hepatocytes and form schizonts, which are also asexual forms. Schizonts undergo a process of maturation and multiplication known as preerythrocytic or hepatic schizogony.
In P vivax and P ovale infection, some sporozoites convert to dormant forms, called hypnozoites, which can cause disease after months or years.
Summarise the epidemiology of malaria.
Malaria is a major health problem in Africa, Asia, Central America, Oceania, and South America. About 40% of the world’s population live in areas where malaria is common.
What are symptoms of malaria?
Travel history
Fever (often cyclical, though falciparum is not)
Diarrhea
Vomiting
Flu-like symptoms
Jaundice
Anaemia
Thrombocytopenia
Time course: Onset usually occurs 7-10 days after inoculation, but may occur after a few months in children.
What are signs of malaria?
Temperature (40 degrees)
Liver may be slightly tender
Splenomegaly
Anaemia
What are appropriate investigations for malaria?
LP to rule out meningitis
Thick and thin blood film
Serology test
What is the management for malaria?
Artesunate is the first line therapy for P. falciparum.
For others seek specialist advice.
What are complications associated with malaria?
Cerebral oedema, seizures, coma, bleeding, anaemia, hypoglucaemia, blackwater fever (haemolysis and acute renal failure)
What is the prognosis of malaria?
Uncomplicated malaria due to P vivax,P malariae, and P ovale has an excellent prognosis. Most patients have a full recovery with no sequelae.
Malaria due to P falciparum is dangerous; if it is not treated quickly and completely, complicated and severe malaria can result, which carries a grave prognosis.
Define thyphoid fever.
Typhoid fever, also known as enteric fever, is a potentially fatal multisystemic illness caused primarily by Salmonella enterica, subspecies enterica serovar typhi and, to a lesser extent, related serovars paratyphi A, B, and C.
Explain the aetiology/risk factors for typhoid fever.
S typhi and paratyphi enter the host’s system primarily through the distal ileum. They have specialized fimbriae that adhere to the epithelium over clusters of lymphoid tissue in the ileum (Peyer patches), the main relay point for macrophages traveling from the gut into the lymphatic system. The bacteria then induce their host macrophages to attract more macrophages.
Summarise the epidemiology of typhoid fever.
Typhoid fever occurs worldwide, primarily in developing nations whose sanitary conditions are poor. Typhoid fever is endemic in Asia, Africa, Latin America, the Caribbean, and Oceania, but 80% of cases come from Bangladesh, China, India, Indonesia, Laos, Nepal, Pakistan, or Vietnam.
What are the signs and symptoms of typhoid fever?
Fever, headache, cough abdominal pain, myalgia followed by GI symptoms a week later.
Splenomegaly, bradycardia, and rosecoloured spots on the trunk.
What are appropriate investigations for typhoid fever?
Blood culture
Urine
Bone marrow aspirate
Serology
PCR
What is the management for typhoid fever?
Third generation cephalosporin or ciprofl oxacin
Adjust therapy following antimicrobial sensitivity testing
