Fleas and related disease

Efficacy of indoor residual spraying using lambda-cyhalothrin for controlling nontarget vector fleas (Siphonaptera) on commensal rats in a plague endemic region of northwestern Uganda

Over the past two decades, the majority of human plague cases have been reported from areas in Africa, including Uganda. In an effort to develop affordable plague control methods within an integrated vector control framework, we evaluated the efficacy of indoor residual spraying (IRS) techniques commonly used for mosquito control for controlling fleas on hut-dwelling commensal rodents in a plague-endemic region of Uganda. We evaluated both the standard IRS spraying (walls and ceiling) and a modified IRS technique that included insecticide application on not only on walls and ceiling but also a portion of the floor of each treated hut. Our study demonstrated that both the standard and modified IRS applications were effective at significantly reducing the flea burden and flea infestation of commensal rodents for up to 100 d after application, suggesting that IRS could potentially provide simultaneous control of mosquito and fleaborne diseases.

Efficacy of a novel formulation of metaflumizone for the control of fleas (Ctenocephalides felis) on cats

A novel spot-on formulation containing metaflumizone (ProMeris for Cats, Fort Dodge Animal Health, Overland Park, KS) was evaluated in five laboratory studies to determine the duration of residual efficacy in cats against fleas after a single spot treatment. In each study, eight domestic shorthair cats were randomly allocated to each treatment group and individually housed. One group in each study remained non-treated. In one study, an additional group of eight cats was treated with a placebo formulation. Cats were treated topically with metaflumizone formulation to provide a dose of at least 40mg metaflumizone/kg. Cats were infested with 100 cat fleas (Ctenocephalides felis felis) once per week for approximately 8 weeks. Cats were comb counted 48h after treatment and each infestation to determine the number of viable fleas present. There were no significant differences in flea counts between the non-treated control and the placebo-treated control (P>0.05) other than a 26% reduction at week 1, demonstrating that the formulation excipients had no activity. Metaflumizone treatment resulted in significantly lower flea numbers relative to non-treated controls on all post-treatment count days (P<0.05). Metaflumizone provided >90% control of flea infestations up to 7 weeks following a single treatment.

Immune dysregulation in flea allergy dermatitis—A model for the immunopathogenesis of allergic dermatitis

BACKGROUND

Flea allergy dermatitis (FAD) is a common skin disease in dogs and can be induced experimentally. It often coexists with other allergic conditions. So far no studies have investigated the quantitative production of cytokine mRNA in skin biopsies and peripheral blood mononuclear cells (PBMC) in flea allergic dogs.

OBJECTIVE

The aim of our study was to improve the understanding of the immunopathogenesis of allergic dermatitis as a response to fleabites.

MATERIAL AND METHODS

Allergic and non-allergic dogs were exposed to fleas. Before and after 4 days of flea exposure mRNA was isolated from biopsies and PBMC. Production of chymase, tryptase, IL-4, IL-5, IL-13, TNF-alpha and IFN-gamma mRNA was measured by real-time RT-PCR. The inflammatory infiltrate in the skin was scored semi-quantitatively. The number of eosinophils, mast cells (MC) and IgE+ cells/mm2 was evaluated to complete the picture.

RESULTS

FAD was associated with a higher number of MC before flea exposure and with a significant increase of eosinophils after flea exposure as compared to non-allergic dogs. The number of IgE+ cells was higher in allergic dogs before and after flea exposure. In allergic dogs mRNA for most cytokines and proteases tested was higher before flea exposure than after flea exposure. After exposure to fleas an increased mRNA production was only observed in non-allergic dogs. In vitro stimulation with flea antigen resulted in a decreased expression of most cytokines in allergic dogs before flea exposure. In contrast, in PBMC, only increased levels of IL-4 and IL-5 mRNA were observed in allergic dogs before flea exposure. However, after flea exposure and additional stimulation with flea antigen the production of mRNA for all cytokines tested was significantly increased in allergic dogs.

CONCLUSION

We demonstrated that the response in biopsies and PBMC is different and that FAD is associated with a TH2 response.

Flea bite hypersensitivity: new aspects on the involvement of mast cells

A study was performed to test the effect of sensitization to flea antigen, followed by exposure to fleas on mast cells (MCs), their subtypes, and IgE+ cells. Biopsies were taken from flea-sensitized dogs (n=28) and non-sensitized dogs (n=5) that had been exposed to fleas. Control groups consisted of flea-sensitized (n=12) and non-sensitized dogs (n=9) that were not exposed to fleas. Biopsies, taken before, 24 and 72 h after local flea exposure, were stained with haematoxylin and eosin (H&E), toluidine blue, a double labelling technique for MC chymase and tryptase and anti-IgE. An intradermal test for flea antigen was performed and serum titres of allergen-specific IgE and IgG were measured. Significantly higher numbers (P<0.001) of double labelled MCs compared to toluidine blue stained MCs were detectable in flea-sensitized dogs independent of flea exposure. In contrast, in non-sensitized dogs, the number of toluidine blue stained MCs and the number of double labelled MCs did not differ. In flea-sensitized dogs after flea exposure the percentage of C-MC was significantly increased at day 1 (P<0.001) and day 3 (P<0.001), whereas the percentage of TC-MCs decreased significantly at day 1 (P<0.001) and day 3 (P<0.05). The percentage of T-MCs decreased (P<0.05 day 0 versus day 1; P<0.05 day 0 versus day 3). No significant difference was detectable after toluidine blue staining and staining for IgE+ cells between the groups nor between the MC density and the number of IgE+ cells. All flea-sensitized dogs had positive skin tests to flea antigen and high serum titres of flea-specific serum IgE and IgG antibodies. In non-sensitized dogs, these results were negative. Our data provide strong evidence for an upregulation of MC proteases during the process of sensitization and a generalized selective release of mast cell tryptase after exposure to the antigen.

Evaluation of the effects of selamectin against adult and immature stages of fleas (Ctenocephalides felis felis) on dogs and cats

The adulticidal, ovicidal, and larvicidal effects of selamectin against flea (Ctenocephalides felis felis) infestations on dogs and cats were evaluated in a series of seven controlled and masked studies (three in cats, four in dogs). Animals were randomly allocated to treatment with either selamectin at a minimum dosage of 6mgkg(-1) in the commercial formulation or one of two negative-controls (0.9% NaCl solution or the vehicle from the commercial formulation). Treatments were administered topically in a single spot on the skin at the base of the neck in front of the scapulae. Speed of kill, measured by flea comb counts at 12h intervals during the 48h immediately following a single treatment on day 0, was evaluated in two studies. One study was in dogs and the other in cats, and each animal was infested with approximately 100 unfed viable adult fleas prior to treatment. Reductions in geometric mean flea counts for selamectin compared with saline were >98% between 24 and 36h after treatment in dogs, and between 12 and 24h after treatment in cats (P< or =0.0006). Efficacy in reducing flea egg hatch and larval development was evaluated in four studies, in which dogs and cats were treated once on day 0 and then repeatedly infested with approximately 600 fleas. Flea eggs were collected approximately for 72h after each infestation, on days 3, 7, 14, 21, and 30, counted, and cultured to determine their hatchability and subsequent larval development. Compared with the vehicle, selamectin was highly effective in reducing flea egg hatch (>92% in cats) and larval development (> or =95% for dogs and cats), and emergence of adults (97.8-100% for dogs, 85.6-100% for cats) for 30 days. Effects of exposure to hair coat debris were investigated in a study with dogs treated once on day 0 and repeatedly infested with 100 adult fleas. Debris (dander, flea faeces, hair, scales) was collected on days 1, 7, 14, 21, and 30 and added to normal flea eggs or larvae for incubation. Compared with debris from vehicle-treated dogs, debris from selamectin-treated dogs was highly effective in preventing egg hatch (>96%), in killing larvae (>98%) and in preventing larval development to adults (>99%) (P</=0.0033). Selamectin was shown to be highly effective in the treatment and control of flea infestations (C. felis) on dogs and cats. The adulticidal, ovicidal, and larvicidal effects of selamectin will be important in interrupting the flea life cycle by preventing the introduction and establishment of new flea infestations in a household environment.

The biology, ecology, and management of the cat flea

The cat flea, Ctenocephalides felis felis, is the most important ectoparasite of domestic cats and dogs worldwide. In addition to its annoyance to pets and humans, C. felis felis is responsible for flea bite allergy dermatitis and the transmission of dog tapeworm. The abiotic and biotic factors that affect the development of immature stages are reviewed with special emphasis given to those aspects directly affecting control. Factors influencing host selection and feeding by adults are summarized. Recent studies concerning mating and oviposition, especially as they impact the likelihood of survival by immatures, are discussed. There has been an increase in the number of reports of insecticide resistance in the past ten years. Greater attention has been placed on disrupting larval development in modern IPM programs. The immature stages of the cat flea are extremely susceptible to environmental factors such as temperature and relative humidity and insect growth regulators (IGRs). In recent years, the control of cat fleas has increasingly relied on the use of IGRs applied to the host or to the indoor environment. Finally, we discuss advances in pesticide chemistry that provide tools for better control of adult fleas on the host.

Flea species from dogs and cats in northern Greece: environmental and clinical implications

Fleas were identified after being collected from 129 dogs and 38 cats of random breed, sex and age. All these animals, infested with fleas and admitted to the Clinic of Medicine of the Veterinary Faculty in Thessaloniki for routine procedures, were from different habitats and originated from various parts of northern Greece. Ctenocephalides canis was the most common species found on the dogs (71.3%). Conversely, its prevalence in the 14 cats was substantially lower (5.3%). Ctenocephalides felis was found on 97.4% of the cats and 40.3% of the dogs surveyed. Of the other flea species, with much lower prevalence, Pulex irritans (0.8%) and Xenopsylla cheopis (0.8%) were observed only on the dogs. Seventeen dogs (13.2%) and one cat (2.6%) had mixed infestations. Flea-associated dermatoses were observed in 26 dogs (20.2%) and four cats (10.5%). Flea-allergic dermatitis, with its typical manifestations, was seen in ten of the dogs (38.5%) with skin lesions. Three out of four flea-allergic cats presented miliary dermatitis and one symmetrical hypotrichosis.

Cat scratch disease in Connecticut. Epidemiology, risk factors, and evaluation of a new diagnostic test

BACKGROUND

Although cat scratch disease is commonly diagnosed in patients who have unexplained regional lymphadenopathy after encounters with cats, its epidemiology and the risk factors for disease are not clearly defined, and there is no generally accepted diagnostic test.

METHODS

We conducted a physician survey to identify cases of cat scratch disease occurring over a 13-month period in cat owners in Connecticut. We interviewed both the patients (or their parents) and controls matched for age who owned cats. Serum from the patients was tested for antibodies to Rochalimaea henselae with a new, indirect fluorescent-antibody test.

RESULTS

We identified 60 patients with cat scratch disease and 56 age-matched subjects. Patients were more likely than controls to have at least one pet kitten 12 months old or younger (odds ratio, 15), to have been scratched or bitten by a kitten (odds ratio, 27), and to have had at least one kitten with fleas (odds ratio, 29). A conditional logistic-regression analysis found that in kitten-owning households, patients were more likely than controls to have been scratched or bitten by a cat or kitten (odds ratio, 12.4; 95 percent confidence interval, 1.0 to 150). Of 45 patients, 38 had serum samples with titers of 1:64 or higher for antibody to R. henselae, as compared with 4 of 112 samples from controls (P < 0.001). The positive predictive value of the serologic test was 91 percent. Of 48 serum samples from patients' cats, 39 were positive for antibodies to R. henselae, as compared with positive samples from 11 of 29 control cats (P < 0.001).

CONCLUSIONS

Cat scratch disease is strongly associated with owning a kitten, and fleas may be involved in its transmission. The serologic test for rochalimaea may be useful diagnostically, and our results suggest an etiologic role for this genus.

Isolation and in vitro translation of messenger RNA encoding allergens of the cat flea, Ctenocephalides felis

Polyadenylated [poly(A)+] mRNA was isolated from the cat flea, Ctenocephalides felis by oligothymidylic acid-cellulose spin column chromatography and translated in vitro using a cell-free rabbit reticulocyte system. The relative incorporation of 35S-methionine into trichloroacetic acid-precipitable translation products obtained using poly (A+) mRNA was 48.5-fold over control translations performed without added mRNA. SDS-PAGE analysis of the translation products in combination with autoradiography showed that many proteins with apparent molecular weights in the range 14-90 K were synthesized. Immunoprecipitation studies performed using flea-allergic dog sera showed that several of the synthesized proteins corresponded with flea allergens. The allergenicity of the lysates was also confirmed by skin testing.

Characterization of allergens of the cat flea, Ctenocephalides felis: detection and frequency of IgE antibodies in canine sera

Flea allergens, fractionated by polyacrylamide gel electrophoresis and transferred to nitrocellulose, were identified using 20 flea-allergic dog sera in an enhanced chemiluminescent assay for canine IgE antibodies. At least 15 different flea components in the molecular weight range of 14-150 K bound IgE and every serum demonstrated a different pattern of binding. Three of the components with apparent molecular weights of 25, 40 and 58 K were each bound by at least 40% of the sera. No reactivity was seen when normal dog sera were used. These results demonstrate a greater number of flea allergens and a far greater diversity of the IgE antibody response to flea allergens than has previously been described, and suggest that immediate hypersensitivity may be an important mechanism in the pathogenesis of canine flea allergy.

Control of rickettsial diseases

Prevention of rickettsial infections is aimed at individual control and epidemic measures (especially in epidemic typhus), vector and rodent control, milk pasteurization (in Q fever), chemoprophylaxis and immunoprophylaxis. In vector and rodent control, the main obstacle is the rise in resistance to insecticides and rodenticides. For this reason in vector control, apart from insecticides, enhancement of the natural immunity acquired by animals in response to tick infestation and vaccination with concealed tick antigens as well as the use of hormones, chemosterilants and genetic manipulation can also be considered. For short-term high-risk exposure, doxycycline may be an effective prophylaxis of illness but may not prevent infection with scrub typhus or spotted fever group rickettsiae. At present, for specific prevention by vaccination, only Q fever vaccines are available for common use. However, development of subunit vaccines, namely immunogenic rickettsial proteins, cloned and expressed in Escherichia coli, seems to be very promising.

Flea allergy dermatitis

Flea allergy dermatitis is one of the most common causes of pruritus in dogs and cats. The degree of pruritus observed in the allergic animal varies widely and is dependent on numerous factors. Management of the flea-allergic patient is extremely frustrating for the owner and the veterinarian. Establishing an organized flea control program for use on the patient and in the environment will help to avoid frustration when dealing with this common ectoparasite of cats and dogs.