CHARACTERISTICS OF NATURALLY ACQUIRED AVIAN MALARIA INFECTIONS IN NAIVE JUVENILE AFRICAN BLACK-FOOTED PENGUINS (SPHENISCUS-DEMERSUS)

Antibody responses to naturally acquired Plasmodium relictum and P. el ongatum infections, blood parasitemia, and disease signs were investig ated in 23 naive juvenile African black-footed penguins (Spheniscus de mersus). Anti-Plasmodium spp. immunoglobulins were detected by enzyme- linked immunosorbent assay (ELISA) using P. falciparum antigens. Ah bi rds rapidly developed antibody to P. relictum and P. elongatum. Five p enguins showed detectable parasitemia and signs of the disease. Parasi temia was not related to the timing of the maximal antibody response o r to the antibody titer. Two of the five parasitemic birds died and gr oss examination revealed splenomegaly, hepatomegaly, and congested, ed ematous lungs. Although the other 17 birds were clearly exposed to the disease, none showed signs of infection. No subsequent episode of par asitemia was observed in individual penguins. A comparison of the fate of 1993 penguins with those from other years showed a great variabili ty in the proportion of birds exhibiting signs of malaria.