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Immunological and epidemiological investigations into avian malaria in the African penguin during rehabilitation and in breeding colonies

Thiart, Hanlie (2005-04)

Thesis (MSc)--University of Stellenbosch, 2005.


ENGLISH ABSTRACT: The African penguin, which occurs along the south-eastern and south-western shores of South-Africa and Namibia, has experienced a severe reduction in population numbers due to guano and egg collection in the first half of the 19th century, and oil pollution in the second half of the 19th century as a result of oil tankers rounding the Cape of Good Hope. The population would have been reduced by a further 19% had it not been for the rehabilitation of penguins at the South African National Council for the Conservation of Coastal Birds (SANCCOB) facility. Although this has been very successful, mortalities as a result of avian malaria infection have considerably reduced the efficiency of rehabilitation. In an effort to assess the role of immunity against malaria in combating the disease, an enzyme-linked immunosorbent assay (ELISA) for the detection of antibody levels to avian malaria was developed. The ELISA was used to detect antibody levels to avian malaria of penguins on entry and during rehabilitation from October 2001 to January 2003. The aim of this study was to continue the determination of antibody levels to avian malaria of penguins entering the SANCCOB facility, in order to allow an evaluation of the antibody levels to avian malaria for two full calendar years. This investigation was combined with a polymerase chain reaction (PCR)-based method, capable of detecting any Plasmodium species in penguin serum. These two methods were also used to investigate avian malaria in several breeding colonies in order to assess the role avian malaria may play in the survival of the African penguin in the wild. Results indicated that the ability of penguins to produce anti-Plasmodium antibodies was not influenced by oiling and that infection with malaria was not due to recrudescence but rather due to infection via mosquitoes. This indicated a possible role of the SANCCOB facility in exposing the penguins to avian malaria. However a large number of penguins arrived at the facility previously infected with malaria, indicating that malaria was present in the breeding colonies. Investigations in the breeding colonies revealed extremely high avian malaria prevalence even though no sick birds or mortalities were observed. This raised the question whether different types of malaria are responsible for infection in the SANCCOB facility and breeding colonies.

AFRIKAANSE OPSOMMING: Die Afrika Pikkewyn kom langs die suid-oostelike en suid-westelike kus van Suid Afrika en Namibië voor. In die afgelope eeu het hierdie spesie ‘n geweldige afname in populasie getalle ondervind. Dit was hoofsaaklik die gevolg van die versameling van guano en pikkewyneiers in die eerste helfte van die 19de eeu en oliebesoedeling in die tweede helfde van die 19de eeu. Die “South African Foundation for Conservation of Coastal Birds” (SANCCOB) is ‘n seevoëlreddings- en rehabilitasiesentrum vir siek, beseerde en ge-oliede pikkewyne. Dit word geskat dat die Afrika Pikkewyn populasie met ‘n verdere 19% sou afgeneem het as dit nie vir die rehabilitasie by die SANCCOB sentrum was nie. Hierdie sentrum het egter aansienlike vrektes in die somer as gevolg van voëlmalaria, wat sodoende die effektiwiteit van die rehabilitasie verlaag. In ‘n poging om die rol van immuniteit teen malaria te bepaal is ‘n “enzyme-linked immunosorbent assay” (ELISA) ontwikkel vir die bepaling van antiliggaam vlakke teen malaria. Hierdie ELISA is gebruik vir die bepaling van die anti-Plasmodium antiliggaam vlakke van die pikkewyne by aankoms en ten tye van rehabilitasie by SANCCOB vanaf Oktober 2001 to Januarie 2003. Die doel van hierdie studie was eerstens om hierdie ELISA bepalings voort te sit om sodoende antiliggaam vlakke teen malaria oor twee kalender jare te kan evalueer. Hierdie ondersoek was gekombineer met ‘n polimerase ketting reaksie (PCR) metode, wat enige Plasmodium spesie in pikkewynserum sou kon opspoor. Hierdie twee metodes is ook gebruik vir ondersoeke in sommige broeikolonies, met die doel om te bepaal watter rol voëlmalaria in die oorlewing van die Afrika pikkewyn in die natuur speel. Resultate het getoon dat olie nie die vermoë van die pikkewyn beïnvloed om anti- Plasmodium antiliggame te vervaardig nie en dat malaria infeksie hoofsaaklik deur muskiete veroosaak word en nie deur heruitbraak van ‘n bestaande infeksie nie. Dit dui egter daarop dat pikkewyne blootgestel word aan voëlmalaria by die SANCCOB sentrum. Daar is ook gevind dat ‘n groot aantal pikkewyne met malaria infeksies by die sentrum opgedaag het wat dui op die voorkoms van malaria in die broeikolonies. Ondersoeke in die broeikolonies het ‘n besonder hoë voorkoms van malaria onthul. Geen vrektes of siek pikkewyne is in die broeikolonies waargeneem nie, wat moontlik kan beteken dat pikkewyne by SANCCOB met ‘n ander tipe malaria geïnfekteer word as in die broeikolonies.

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