The Mazzotti test is based on the clinical response of a patient with onchocerciasis to a test dose of diethylcarbamzine (DEC). It is a result of the host allergic reaction to dead microfilaria. The availability of ELISA serologic tests and PCR have made the test less necessary.


Patient selection: A person suspected of having onchocerciasis with negative results after a complete examination (skin snips, eye exam, etc.)


Dose: 25-50 mg diethylcarbamazine


A positive reaction is development of one or more of the following within a few hours of the dose:

(1) pruritis, which may be severe

(2) variable erythema

(3) ocular reaction (uveitis, other)

(4) systemic allergic response


The use of anti-inflammatory agents and antihistamines can reduce the severity of the reaction.


The reactions may be very severe in a patient with a heavy parasite load. It should not be done on someone with extensive disease if the infection can be diagnosed by another method.


A modification of test with less chance of a serious clinical reaction and therefore better patient acceptance is a patch test with the DEC applied topically. The site of application will develop a localized allergic reaction.


The test should not be done in a patient with allergy to diethylcarbamazine since this would cause a false positive reaction.


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