The Clinical Significance And Manifestations Of Sand Fly Fever And Yellow Fever As Arboviral Infections
The Clinical Manifestation Of Sandfly Fever
Sand Fly Fever (Phlebotomus Fever, Papatasil Fever, 3 Day Fever
It is an acute infectious fever caused by arbovirus transmitted by the sand fly, Phlebotomus papatasil. Among several arboviruses, five are known to produce sand fly fever. The virus is present in the blood of the patient for two days, starting a day before the onset of fever. This disease is present in lots of developing countries, especially in the tropics.
Female phlebotomus sucks blood. It becomes infective 7 days after an infective feed, and remains so for the rest of its life. In the tropical environment, sand flies are active throughout the year. In temperate climates, they are seen only in the summer. In endemic areas, children suffer more. An attack confers type-specific immunity which lasts for about 2 years.
Incubation is 2 to 6 days after which there is abrupt onset of high fever and rigor. The temperature rises rapidly to about 400C with intense headache, malaise, ocular pain, photophobia, giddiness and conjunctival injection. Sometimes, it may be associated with neck rigidity, back pain, bone and joint pains, anorexia, nausea and vomiting. Inititally, there is tachycardia but soon bradycardia sets in. After three days, the fever comes down by crisis. Though the disease may be mistaken for dengue fever, absence of rash and lymphadenopathy helps in supporting the diagnosis of sand fly fever. Aseptic meningitis may occur in 12% of cases.
Diagnosis: The diagnosis is mainly clinical. There is leucopenia. The diagnosis can be confirmed by demonstrating a rise in antibody titer in paired sera.
Treatment: The disease is self-limiting, benign and nonfatal. Symptomatic measures include analgesics and supportive measures. Convalenscence may be prolonged and mental depression may be disabling. Sand flies are controlled by spraying residual insecticides in and around living quarters. Personal protection is achieved by using insect repellants. Due to their small size, sand flies are not effectively kept out by the ordinary mosquito nets.
Clinical Manifestations Of Yellow Fever
This infection is caused by a group B arnovirus transmitted to man by the bite of Aedes mosquitoes. This disease is endemic in many parts of Africa, tropical parts of south America and panama. In endemic areas, monkeys and colonies of infected mosquitoes act as reservoir. Several specieis of aedes mosquitoes act as vectors. An attack confirms life-long immunity. This disease has not been reported in places like India so far, though the vector Aedes aegypii is very prevalent. The disease is notifiable under the International Health Regulation.
Liver and kidneys show maximal lesions, but hemorrhage may occur in all organs. Hepatic changes include widespread necrosis, and degeneration of liver cells. Renal changes include acute tubular necrosis and subscapular hemorrhages.
The incubation period is 3 to 6 days. The classical form which is rare, shows three distinct stages- the initial fever, the period of calm and the subsequent phase of reaction and toxemia. The first stage is due to the direct effect of the virus and the last one is due to hepatic, renal or circulatory complications. Most of the deaths occur at this stage. The disease sets in with high fever, chills, rigor, body aches and severe vomiting. By the fourth day, the temperature comes down and the second stage starts. Many cases recover without going to the third stage.
The third stage of intoxication follows within hours to days in severe cases. There is rise of temperature, bradycardia, jaundice, widespread hemorrhage, and renal failure. Death is due to hepatic or renal failure or peripheral vascular collapse.
Diagnosis: In endemic areas, fever, leucopenia and proteinuria with or without jaundice should suggest the possibility of yellow fever. Specific diagnosis is established by the isolation of the virus from blood in the first few days of the fever or demonstration of rising titer of antibodies in serum. There is no specific treatment. Hepatic and renal failure are to be managed by supportive measures.
Prevention: Vaccination using live attenuated vaccine (17 D strain) is very effective. A single vaccination gives full protection for 10 years. Many countries insist on yellow fever vaccination before entry. Protection starts after 10 days. Though, side effects are generally negligible, children below 9 months of age may develop encephalitis. Pregnancy is not a contraindication for vaccination.
© 2014 Funom Theophilus Makama