Tick Population Dynamics Research Articles

Population dynamics of the American dog tick (Acari: Ixodidae) in relation to small mammal hosts.

The hypothesis was tested that size and composition of small mammal hosts are primary factors influencing the population dynamics of adult American dog ticks, Dermacentor variabilis (Say). We found that white-footed mice, Peromyscus leucopus (Rafinesque), and meadow voles, Microtus pennsylvanicus (Ord), were primary hosts for immature stages of ticks. Seasonal abundance of immature ticks showed a bimodal distribution, the highest population sizes occurring in the spring and late summer. A strong positive relationship between size of adult tick populations and size of small mammal populations, especially of meadow voles, indicated that feeding success of immature ticks is the most important factor regulating adult tick populations. Because numbers of larvae appeared unaffected by changes in numbers of small mammals, population regulation appeared to be determined mainly by the feeding success of the nymphal stages.

Population dynamics of ticks on Ankole cattle in five ecological zones in burundi and strategies for their control

Tick populations were observed on Ankole (Sanga type Bos indicus x Bos taurus) cattle at monthly intervals over periods of 2–3 years in 4 ecological zones (Gatumba (830-m alt., 789-mm rain); Gitega (1671-m alt., 1122-mm rain); Kirundo (1420-m alt., 1076-mm rain) and Gihofi (1260-m alt., 1225-mm rain)) of Burundi, Central Africa. Concurrently, observations were made on the development and survival of Rhipicephalus appendiculatus in pastures at each location. Ticks were also counted on cattle in a fifth, high altitude zone (Ijenda, 2191-m alt., 1549-mm rain) for a period of 2 years. Rainfall was monomodal at all sites and fell between September and May. The species composition and total numbers of ticks infesting cattle in the 5 ecological zones varied. The most common species recorded were R. appendiculatus, Boophilus decoloratus and Amblyomma variegatum. The highest average number of adult females of the above species completing engorgement daily was 29 R. appendiculatus at Kirundo, 13 B. decoloratus at Ijenda and A. variegatum at Gitega. The regions differed slightly in their overall level of tick infestation, as measured by the average numbers of adult female ticks of all species engorging daily, i.e. Kirundo (34), Gatumba (27), Gitega (26), Ijenda (21) and Gihofi (11). Adults of A. variegatum exhibited the strongest seasonal pattern of feeding, with peaks early in the wet season. Non-climatic factors were apparently important in determining the relative numbers of A. variegatum in different regions. Development times of the free-living stages of R., appendiculatus in pastures varied between locations, taking 3 weeks for engorged larvae, 4–7 weeks for nymphs and 6–9 weeks for oviposition and egg development. Engorged larvae and nymphs suffered the least mortality while egg hatching was reduced in the dry season. Fifty percent of unfed larvae survived 1.5–3 months, nymphs 3–5 months and adults 16 months. Parasitic ticks completed engorgement more successfully when attached in preferred sites on the host's body. Computer simulations were used to estimate the proportional reduction in numbers of R. appendiculatus from dipping strategies with different timing, duration and efficiency. Strategies of 3-months duration, with the start timed to coincide with the period of adult feeding activity, were economically the most efficient. Computer simulations suggested that the annual cattle migration from the highlands to the lowlands in the dry season was important in limiting the size of tick populations. These results were taken into account when designing a policy to make the best use of the country's resources.

Dynamics of African tick (Acari: Ixodoidea) populations in a natural Crimean-Congo hemorrhagic fever focus.

A study of ticks collected from large and small mammals and from vegetation in an area where Crimean-Congo hemorrhagic fever (CCHF) virus was found was carried out over 3 yr. Three two-host species of ticks, Hyalomma marginatum rufipes Koch, Hyalomma truncatum Koch, and Rhipicephalus evertsi evertsi (Neumann), were abundant; and three other species, Amblyomma marmoreum Koch, Margaropus winthemi Karsch, and Argas, undescribed sp., were less frequently encountered. Immatures of H. m. rufipes and H. truncatum showed two peaks of activity, one in July and one in November; adults were most active during December, January, and February. A similar pattern of seasonal activity was found for larvae and nymphs of R. e. evertsi, which showed peaks in their occurrence in May and in October/November. H. m. rufipes adults were more common on eland and Burchell's zebra, but H. truncatum preferred black wildebeest. Immature stages of these species also showed host preference. H. truncatum was very common on rodents and hares and absent from guinea fowl; H. m. rufipes was found on guinea fowl and also on hares, but not on rodents. Seasonal activity of ticks, the hosts with which they are associated, and their role in the epidemiology of CCHF are discussed.

Species quantification and seasonal abundance of ticks (Acarina: Ixodidae) in the eastern province of Zambia: Ticks from cattle

Abstract Ticks from cattle were collected for the purposes of quantifying the number of tick species and their relative abundance at Msekera Regional Research Station. Fifteen species were recorded. It was found that although different species of ticks parasitized cattle throughout the year, their peaks of abundance were dependent on the season. The majority of the species had their peaks during the wet season (November to April). Rhipicephalus punctatus (Warburton) was found to be the most abundant species followed by Rhipicephalus appendiculatus (Neumann) and Amblyomma variegatum (Fabricius). Haemaphysalis leachi (Audouin) and Rhipicephalus turanicus (Morel and Vassileades) were least abundant. The findings are discussed in relation to seasonal vector abundance and disease transmission, the problems of chemical control of a multi‐species tick population and climatic influence on general tick population dynamics.

Dynamics of tick populations (acari: Ixodidae) in the Eastern Cape Province of South Africa.

A survey of ixodid ticks collected from livestock and from vegetation in the Eastern Cape Province of South Africa was carried out over a 5-year period. Five species, Rhipicephalus appendicidatus, Amblyomma hebraeum, Boophilus decoloratus, R. evertsi evertsi and Haemaphysalis silacea , were relatively abundant and 3 other species, R. s. simus, R. glabroscutatum , and Ixodes pilosus , were much less frequently encountered. R. appendicidatus showed a definitely seasonal pattern of activity. Larvae were present mainly during the early winter (April to June) and nymphs were active mainly during winter (July/August). Adult numbers increased sharply beginning in November, reached a peak in the late summer months (January/February), then decreased and finally disappeared in May. This tick was more common in bushy habitats than in open areas. A. hebraeum demonstrated a similar pattern of seasonal activity and like R. appendiculatus was abundant in humid habitats. B. decoloratus, R. e. evertsi and H. silacea were present throughout most of the year, and although they did not show a definite pattern of occurrence, they were more abundant during midsummer and midwinter. Seasonal activity, population size and dynamics of tick populations for each species from various habitats are presented. Patterns of activity are shown to be regulated by photoperiod and/or temperature, while population sizes are generally governed by humidity.