The Pfeiffer Reaction with Leptospira in Yellow Fever

Andrew Watson SellardsLaboratory of the Service for Rural Sanitation and Prophylaxis of the State of Parahyba, The Department of Tropical Medicine, Harvard Medical School, Boston, Massachusetts, Brazil

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The serum from 11 patients examined about three and one-half months after recovery from typical yellow fever gave negative Pfeiffer reactions to L. icteroides and L. icterohaemorrhagiae. As controls for these negative tests, the serum of 2 guinea pigs immune to L. icterohaemorrhagiae gave positive Pfeiffer reactions with L. icteroides and L. icterohaemorrhagiae. These results, therefore, furnish additional evidence of the identity of L. icterohaemorrhagiae and L. icteroides.

A striking characteristic of leptospiral infections is the development and persistence in the blood of immune substances which are easily demonstrable by the Pfeiffer phenomenon; these 11 cases of yellow fever failed to show this phenomenon and it is one which is vital for the acceptance of L. icteroides as the etiologic agent of yellow fever. Nevertheless this failure leads to certain constructive considerations.

The lack of any etiologic relationship of L. icteroides to yellow fever is of definite significance in determining public health measures for the control of this disease. If L. icteroides were the causative agent of yellow fever we would be confronted with the possibility of an almost unlimited animal reservoir in rodents under circumstances that would be very discouraging for the ultimate extermination of yellow fever from a community.

The occurrence of negative Pfeiffer reactions in typical cases of yellow fever facilitates the problem of determining the nature of the disease described in Africa as yellow fever. From time to time serious doubt has been expressed as to whether true yellow fever occurs in Africa although cases have been described which clinically and pathologically are characteristic. A negative Pfeiffer reaction with leptospira definitely tends to confirm rather than to refute the diagnosis of yellow fever.

Some important questions are brought into sharp relief. Investigations from various countries make it evident that leptospiral infections are primarily a disease of rodents with occasional off-shoots in man notably in the form of Weil's disease but not as yellow fever. It becomes necessary to review anew the evidence of the susceptibility to yellow fever of the guinea pig, mouse, rat, dog and monkeys as tested by the injection of L. icteroides or of specimens of blood from yellow fever cases. One must give serious consideration to the older view that the virus of yellow fever is limited in nature to its cycle in man and the mosquito.