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
What are complications associated with typhoid fever?
GI perforation
Myocarditis
Hepatitis
Nephritis
What is the prognosis of typhoid fever?
The prognosis among persons with typhoid fever depends primarily on the speed of diagnosis and initiation of correct treatment.
Generally, untreated typhoid fever carries a mortality rate of 10%-20%. In properly treated disease, the mortality rate is less than 1%.
Define dengue fever.
Dengue is the most common and important arthropod-borne viral (arboviral) illness in humans. It is transmitted by mosquitoes of the genus Aedes, which are widely distributed in subtropical and tropical areas of the world.
Explain the aetiology/risk factors for dengue.
Dengue infection is caused by dengue virus (DENV), which is a single-stranded RNA virus.
Living in endemic areas of the tropics (or warm, moist climates) where the vector mosquito thrives is an important risk factor for infection.
Summarise the epidemiology of dengue.
The overall incidence of dengue, as well as the explosive outbreaks of dengue, has been increasing dramatically over the last several years.
Older data suggested an estimated 50-100 million cases of dengue fever and 500,000 cases of dengue hemorrhagic fever occur worldwide, with 22,000 deaths (mainly in children).
What are symptoms of dengue?
History of living, or travelling to a region where the disease is endemic.
Children younger than 15 years usually have a nonspecific febrile syndrome, which may be accompanied by a maculopapular rash.
Classic dengue fever begins with sudden onset of fever, chills, and severe (termed breakbone) aching of the head, back, and extremities, as well as other symptoms.
The fever lasts 2-7 days and may reach 41°C. Fever that lasts longer than 10 days is probably not due to dengue.
What are signs of dengue?
The clinical description of dengue fever is an acute febrile illness of 2-7 days duration associated with 2 or more of the following:
- Severe and generalized headache
- Retro-orbital pain
- Severe myalgias (especially in lower back, arms and legs)
- Leukopenia
- Characteristic rash
- Arthralgias of knees and shoulders
What are appropriate investigations for dengue?
FBC
LFTs
Coagulation studies
USS
What is the management for dengue?
Dengue fever is usually a self-limited illness.
There is no specific antiviral treatment currently available for dengue fever. Supportive (fluid intake, analgesics).
Prevention is key: Mosquito nets, mosquito repellant, remain in well air conditioned places.
What are the complications of dengue?
Dengue hemorrhagic fever
Dengue shock syndrome
What is the prognosis of dengue?
Mortality rate of less than 1%.
When treated, dengue hemorrhagic fever has a mortality rate of 2-5%.
When left untreated, dengue hemorrhagic fever has a mortality rate as high as 50%.
Survivors usually recover without sequelae and develop immunity to the infecting serotype.
