Ectoparasites of dogs in home environments on the Caribbean slope of Costa Rica

Reports on ectoparasites on dogs in Central America are scarce. The aim of this study was to identify flea, louse and tick species infesting dogs in home environments on the Caribbean slope of Costa Rica, and determine their frequency and coexistence. Ectoparasites were collected from dogs in 83 rural homes at five study sites. Specimens were identified and separated according to species. Fleas were the most common ectoparasite (G  =  22,217, DF  =  8, p  =  0.004). Ctenocephalides  felis and Pulex  simulans were found in 83% and 55% of the homes with ectoparasites, respectively. Trichodectes canis (13%), Heterodoxus spiniger (10%), Rhipicephalus sanguineus (18%), Rhipicephalus (Boophilus) microplus (5%) and Amblyomma ovale (8%) were also present. More than one species was collected in most cases (66%), and the most common combination was C. felis and P. simulans (59% of homes with fleas). The high frequency of P. simulans emphasizes the need for adequate identification. This was the first study involving different ectoparasites of dogs in Costa Rica, as well as the first report of T.  canis in this country. The relative frequency and coexistence of these ectoparasites in the home environment may have implications for animal and human health.

Fleas (Siphonaptera), lice (Pthiraptera) and ticks (Ixodida) have long been recognized as important groups of arthropods that infest mammals, including domestic dogs, Canis lupus familiaris (BOWMAN, 1995).The most common fleas on dogs are Ctenocephalides felis and Ctenocephalides canis, although Pulex irritans and Pulex simulans can frequently be encountered (DURDEN et al., 2005;BECK et al., 2006).The lice include the chewing lice Heterodoxus spiniger and Trichodectes canis, as well as the biting louse Linognathus setosus (GONZÁLEZ et al., 2004).Different tick species infest domestic dogs depending on the geographical area; however, one of the most widely distributed is Rhipicephalus sanguineus (DANTAS-TORRES, 2008).Although most of these ectoparasites are considered to be cosmopolitan, many species show differences in prevalence depending on the particular geographical area.For instance, C. canis is frequently found on dogs in European countries and in some areas of South America (GONZÁLEZ et al., 2004;XHAXHIU et al., 2009), although it can be rare in other countries.A similar scenario can be depicted for specific populations of other fleas, lice and ticks.
The presence of ectoparasites on a dog can have a negative impact on the animal's health.Fleas are usually associated with dermatitis and allergic reactions with varying degrees of severity (KOUTINAS et al., 1995).Fleas, ticks and sucking lice exhibit hematophagic behavior, and some species act as intermediate hosts and/or vectors of pathogens such as Ehrlichia spp., Anaplasma spp., Rickettsia spp., Borrelia spp., Bartonella spp., Babesia spp.and Dipylidium caninum (BOWMAN, 1995;GONZÁLEZ et al., 2004).Furthermore, many pathogens transmitted by fleas and ticks of dogs are considered to be zoonotic and may affect humans.
In Central America, knowledge of dog ectoparasites and their contact with humans is limited.Recent scientific papers about this particular topic are scarce, and those available for Costa Rica and most of Central America are restricted to new records or specific groups of ectoparasites (VARGAS; MÉNDEZ, 1987;ALVAREZ CALDERÓN et al., 2005;ÁLVAREZ et al., 2006).To our knowledge, there are no specific studies in Costa Rica on flea and louse populations in domestic dogs.This paper describes the species of fleas, lice and ticks of domestic dogs present in home environments on the Caribbean slope of Costa Rica.This provides useful evidence for the veterinary community in terms of the relative frequencies and coexistence of ectoparasites, as well as support for future studies aiming to make links to some of the potential pathogens transmitted to these species in this region.
Homes were selected using a non-probabilistic approach and mainly included households located in rural settings with nearby forested areas.In addition, they were at least 100 m from each other, had one or more dogs that were allowed to roam freely in and around the home, and presented any of the ectoparasites of interest on at least one dog.Considering that dogs in home environments are in close contact with each other and probably share the same ectoparasite species, the analysis was performed by pooling samples of one to three dogs from the same home instead of using samples from individual dogs.This reduced the errors attributable to lack of independence between dogs that share homes, as well as differences in total numbers of dogs per home.
Fleas, lice and ticks were collected using combs and tweezers during a period no longer than one man-hour per home, and were placed in 70% ethanol for transporting to the laboratory.The specimens were separated and grouped into batches according to species, collection site and specific household.They were identified by observing key characters, and some specimens were cleared in lactophenol and mounted in Hoyer's medium when this was required to confirm species identification (HOPKINS; ROTHSCHILD, 1953;SMIT, 1958;EMERSON;PRICE, 1975;BARROS-BATTESTI et al., 2006).Variations in frequency between different groups of ectoparasites were analyzed using a G-test.In addition, a chi-square test was used to determine whether the frequencies of flea species differed (SOKAL; ROHLF, 1994).An alpha value of 0.05 was used in all tests, and analyses were performed in JMP ® 7.0 (SAS Institute, Inc.).
Ectoparasites were collected from a total of 83 rural homes.Fleas, lice and ticks were observed on dogs at the five study sites (Table 1).Overall, fleas were the most frequent ectoparasite found (G = 22,217, DF = 8, p = 0.004).Ctenocephalides felis was present in 83% of the households, and it was the most common ectoparasite in the home environments of all of the sites evaluated.Pulex simulans was identified in 55% of the homes with ectoparasites, and it was also widespread at the study sites.The brown dog tick, R. sanguineus, was found in 18% of the homes, while Amblyomma ovale (8%) and Rhipicephalus (Boophilus) microplus (5%) were less frequent.The chewing lice, T. canis and H. spiniger, were present on dogs from 13% and 10% of the homes, respectively.
Only 28 (34%) of the homes had a single species present, and it was usually C. felis.Two species were present simultaneously in 36 (43%) of the households, and C. felis plus P. simulans was the most common combination.Sixteen homes (23%) had three or more ectoparasites present, and the combination of C. felis, P. simulans and H. spiniger was the most frequent.
Coexistence of C. felis and P. simulans was common at all sites (Figure 1).Out of 69 homes in which fleas were found on dogs, 41 (59%) had both species, while 28 (40%) only had C. felis and five (7%) only had P. simulans.Considering the frequency of each species observed in homes with fleas, the likelihoods of finding C. felis versus finding P. simulans were not significantly different (χ 2 = 1.852,DF = 4, p = 0.763).
Most of the ectoparasites that were found on the Caribbean slope of Costa Rica have also been reported elsewhere in Central America The flea and tick species detected in this study may also be associated with transmission of animal and human pathogens such as Ehrlichia canis and Rickettsia felis, which have already been identified respectively in R. sanguineus and C. felis in Costa Rica (ROMERO et al., 2011;HUN et al., 2011).The presence of these and other dog ectoparasites in home environments may suggest that there is high potential for transmission of pathogens.The relative frequencies and coexistence of ticks with fleas and lice, as well as their proximity to human dwellings demonstrate possible implications for animal and human health in a region where information about ectoparasites of domestic animals is scarce.