Visceral Leishmaniasis: Health Significance Of Its Immunology And Clinical Presentations
Kala Azar Clinical Presentations
Clinical Manifestations Of Visceral Leishmaniasis
The incubation period is commonly 2 to 6 months, but in exceptional cases it may be longer. The onset may be insidious as in typhoid or abrupt as in malaria. In the enteric type, fever reaches its height in 1 to 2 weeks, and persists continuously. Later, the temperature comes down by lysis to normal. Following this febrile phase there is a period of apyrexia lasting for 2 or 3 weeks (up to 2 months). Relapse of fever occurs thereafter. At this time fever may be remittent or intermittent. In the cases with malaria-like onset, paroxysms of fever with chills and rigor repeat everyday. The fever comes down after a few weeks and the periods of pyrexia and apyrexia alternate for several months. In cases with insidious onset, the main complaint may be vague illhealth with only mild fever without any characteristic pattern.
An occasional patient may show two peaks of fever in 24 hours, this double rise is very suggestive of Kala-azar. Despite the fever, this patient feels well and has a good appetite. Unlike enteric fever, gastrointestinal and respiratory complications are absent.
The spleen enlarges to become palpable by three weeks and in six months it reaches the umbilicus. Initially, it is soft, later or it becomes firm. The liver is moderately enlarged (2.5 to 10cm), firm and non-tender. Lymph nodes may be moderately enlarged in Kala-azar. Lymphadenopathy is a prominent feature in African cases. As the disease progresses, weight loss and anemia become pronounced. Chronic cases of more than 6 months duration present a characteristic facies. This consists of emaciation with thin drug lusterless and brittle hair, dry rough skin, and pigmentation around the mouth, nose, forehead and temples. Hepatosplenomegaly results in enlargement of the abdomen. Edema of the ankles and ascites as epistaxis and bleeding from the gums. The teeth may fall off.
Immunity In Visceral Leishmaniasis
Immunology Of Kala-azar
Kala-azar produces a humoral immune response. Immunoglobulins G and M are markedly increased, IgG being relatively more increased with IgG being relatively more increased. Both IgG and to a lesser extent IgM contain antibodies against the parasite. Though, these antibodies are demonstrable in a high proportion of cases, their diagnostic value is not firmly established. With successful treatment, the IgM values come down quite early but the IgG levels take a few months to fall to normal. Cell-mediated immunity is impaired. I lymphocytes, migration inhibition factor (MIF) and lymphocyte transformation index are diminished in active Kalar-azar. CMI returns to normal with successful therapy. Leishmanin skin test is negative during active Kala azar, but it becomes positive 6 to 12 months after full recovery.
© 2014 Funom Theophilus Makama