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1.
Int J Parasitol ; 35(4): 391-6, 2005 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-15777915

RESUMO

Sero-epidemiological surveys involving 27,526 cattle over a period of 8 years show that Theileria parva, the parasite causing East Coast fever (ECF) is found throughout southern Zambia. Higher values of T. parva sero-prevalence were observed in the plateau districts of Monze, Choma and Mazabuka than in the valley districts of Siavonga and Sinazongwe. Our results reveal a strong association between high T. parva sero-prevalence and the presence of the periodic climatic phenomenon known as the El Nino Southern Oscillation. More T. parva sero-positive samples were recorded during El Nino years (1997/98) (P<0.001) than other years in the study period. From this association, we conclude that Multiple El Nino Southern Oscillation Indices can be used to predict years with high or low ECF infection prevalence thereby contributing to the improved control of ECF in the area.


Assuntos
Conceitos Meteorológicos , Theileria parva , Theileriose/epidemiologia , Animais , Bovinos , Técnica Indireta de Fluorescência para Anticorpo/veterinária , Água do Mar , Estudos Soroepidemiológicos , Movimentos da Água , Zâmbia
2.
J Vector Ecol ; 29(2): 347-54, 2004 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-15707294

RESUMO

We examined the relationship between body size and the phenology of the tick complex Rhipicephalus appendiculatus/Rhipicephalus zambeziensis. These ticks transmit Theileria parva in cattle. In Africa, the body size of R. appendiculatus increases with latitude while the body size of the morphologically similar Rhipicephalus zambeziensis is constant at two different latitudes. A larger body size is necessary once survival becomes a constraint. The most plausible explanation for the smaller R. appendiculatus in equatorial Africa is the cost to produce a larger egg. The consequences of these findings for the introduction of R. appendiculatus in new environments are discussed. New field observations from southern Zambia indicate that R. appendiculatus body size does not vary seasonally as compared to eastern Zambia. This is an additional indication of the presence of a single diapausing population of larger ticks.


Assuntos
Rhipicephalus/anatomia & histologia , Theileriose/transmissão , Animais , Tamanho Corporal , Bovinos , Demografia , Feminino , Geografia , Oviposição , Rhipicephalus/parasitologia , Zâmbia , Zimbábue
3.
Exp Appl Acarol ; 41(1-2): 115-28, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17288005

RESUMO

The closely related species Rhipicephalus appendiculatus and R. zambeziensis co-occur in a wide area in Zambia. In this area, specimens of both species have been collected on the same individual host at the same time. In addition, specimens that are morphologically intermediate between R. appendiculatus and R. zambeziensis have been found in this area. These observations cast some doubt on the species status of R. appendiculatus and R. zambeziensis. Because the two taxa have varied influences on the epidemiology of East Coast fever (ECF), a cattle disease for which they act as vectors, it is essential that their taxonomic status is clarified and their identification is accurate. Therefore a phylogenetic analysis of nucleotide sequences of the ITS2 and a fragment of the mitochondrial 12S rDNA was performed to reassess the specific status of both taxa. This revealed two well supported clades coinciding with R. appendiculatus and R. zambeziensis as two separate species. In order to facilitate species identification a PCR-RFLP diagnostic assay was developed based on BauI digestion of the ITS2 gene. This assay produced clear diagnostic banding patterns for the two species and is applicable over a wide range of both species' distribution.


Assuntos
Ixodidae/classificação , Ixodidae/genética , Animais , Sequência de Bases , DNA Mitocondrial/genética , DNA Espaçador Ribossômico/genética , Filogenia , Polimorfismo Genético , Especificidade da Espécie , Zâmbia
4.
Med Vet Entomol ; 16(4): 430-41, 2002 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-12510896

RESUMO

Distribution data for epidemiologically important ticks (Acari: Ixodidae) in the Southern Province of Zambia, one of the main cattle areas of the country, are presented. Boophilus microplus (Canestrini) was not recorded in southern Zambia, whereas Boophilus decoloratus (Koch) is present throughout the area. New distribution patterns for less economically important ixodid ticks are also discussed. Southern Zambia is a transition zone because it is the most northern area in Africa where mixed Rhipicephalus appendiculatus Neumann and Rhipicephalus zambeziensis Walker, Norval & Corwin populations were reported. Although a second generation of adult R. appendiculatus/R. zamnbeziensis was encountered, simulations indicated that this phenomenon is very rare in southern Zambia, mainly because of the colder temperatures during the early dry season and lower rainfall. These simulations were supported by a development trial under experimental conditions. Tick body size measurements showed that southern Zambian ticks are larger than eastern Zambian R. appendiculatus. It is hypothesized that body size is related to diapausing intensity in this species. The epidemiological consequences are that a different approach to control Theileria parva (Theiler) (Piroplasmida: Theileriidae) and other tick-borne diseases is needed in southern Zambia, compared to the one adopted in eastern Zambia.


Assuntos
Ixodidae/fisiologia , Animais , Bovinos , Clima , Coleta de Dados , Feminino , Ixodidae/classificação , Estágios do Ciclo de Vida , Estudos Longitudinais , Dinâmica Populacional , Chuva , Estações do Ano , Temperatura , Zâmbia
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