For the flea, its biology makes it a very efficacious vector of many pathogens (Genchi, 1992). In towns, the cat flea is mainly synanthropic and maintains its life cycle indoors feeding on pets (Genchi, 1992). However, it must be emphasised that only about 5% of the flea population lives and feeds on the animals, the remaining 95% (eggs, larvae and pupae) are spread around indoor habitat. In buffered microclimate situations such as buildings in towns, cat flea populations grow throughout the year, showing unexpected large peaks caused by the sudden breakdown of nymphal diapause of a very large number of individuals, when habitations are abandoned by domestic animals and their owners for longer or shorter times (Genchi, 1992).
The reasons that the cat flea is such an extremely successful and ubiquitous parasite are the wide range of possible hosts and its status as a rather permanent parasite (Dryden, 1993; Grant, 1996). Altogether, the cat flea has been found on more than 50 hosts throughout the world (Hopkins and Rothschild, 1953; Williams, 1986).
Since all the life cycle stages of C. felis are susceptible to desiccation, only those eggs that fall into protected microhabitats hatch larvae that will ultimately develop into adults (Dryden, 1989). As stated by Byron (1987), suitable breeding sites are not widespread in homes but confined to specific sites. Areas that may be suitable for flea development in the house are (Dryden, 1989):
- pet’s bedding
- thick shag carpet
- carpeted or dirt floor basements
Potentially favorable developmental sites outside occur where there is moist soil and shade:
- dog houses
- flower beds
- areas under bushes
- damp crawl spaces
- any places where the flea-infested animal might rest during the heat of the day
Areas in the house such as wood or tile floors and well-traveled hallways are less likely to support development. Likewise, open areas of the lawn that are exposed to prolonged sunlight offer poor growth conditions (Dryden, 1989). Summarising, significantly more fleas are found in rooms where pets spend most of their time resting (Osbrink et al., 1986).
Opportunities of flea exchange are created by host movement and interaction (Marshall, 1981). In this context the ranges of pets, as well as wild life, have to be considered. Cats can have home ranges in urban areas of <1 ha or up to 270 ha rurally, depending on cat density and the availability and distribution of food (Liberg and Sandell, 1988). Urban dogs may have home ranges of 1.5-2.6 ha (Beck, 1973). Wild animals are mobile, increasingly abundant in urban areas and often serve as alternative hosts for the cat flea (Bossard et al., 1998).
The abundance of adult cat fleas fluctuates with seasonal changes. The warm months of spring and summer give rise to the highest numbers, whereas few are found during the cold months of late fall and winter (Metzger and Rust, 1997). Infestations of cat fleas consistently recur during the warm months of the year (Osbrink and Rust, 1985). No life stage of the cat flea can survive extended periods of subfreezing temperatures, and no reports of a diapausing stage exist (Silverman and Rust, 1983). Therefore two hypotheses have been proposed as possible over-wintering strategies of cat fleas (Metzger and Rust, 1997):
- Feral mammals, whose territories extend into urban areas, harbour cat fleas all year and represent the source of reinfestation for domestic animals (Dryden and Rust, 1994).
- An unknown percentage of preemerged adults remain inside the cocoons for extended periods and emerge when conditions are favorable for immature development.
The survival and maintenance mechanisms of C. felis, important for epidemiological considerations, can be summarised as follows (Rust and Dryden, 1997):
- The presence of adults on domestic and feral cats and dogs.
- The presence of adults on urbanised small wild mammals (such as raccoons and opossums).
- A delayed development of immature stages in freeze-protected underground dens of wildlife.
- A delayed development of pupae and emergence of adults in the home environment.
- Beck AM: The ecology of stray dogs. 1973, York, Baltimore
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