Management of Outbreaks and Their Prevention
In most cases, animal dermatophytoses are self-limiting diseases because innate and/or acquired immunity is strong enough to control the spread of infection. Nevertheless, specific treatment is required to obtain a more rapid clinical cure, to minimize contamination to other hosts (including humans) and to reduce the dissemination of infective arthroconidia in the environment.
Recommendations for the treatment are based on both in vivo and in vitro investigations (Moriello et al. 2017). These recommendations systematically include the disinfection of the environment and the limitation of contact between infected animals and healthy ones.The transmission of zoophilic dermatophyte is through direct contact with infected animals or through contaminated environments, and limiting this kind of contact is a simple way for the prevention of transmission (Chermette et al. 2008). Sometimes prevention is difficult to perform. In case of subclinical infection or mechanical carriage, animals have no cutaneous lesions but may be responsible for contamination. Such a situation is frequently reported in some animal populations (e.g., cats infected by M. canis or guinea pigs infected by T. benhamiae).
The use of antifungals has been proposed for the prevention of animal dermatophytosis. However, investigations showed that the oral administration of griseofulvin did not allow the prevention of infection in humans. Topical administration of antifungal drugs seems to be more appropriate. When an animal has been in contact with an infected animal or area, it could be useful to use an antifungal shampoo.
Efforts in developing fungal vaccines to prevent dermatophytosis in different animal species are going on (Lund and DeBoer 2008; Mignon et al. 2008; Moriello et al. 2017). Immunoprophylaxis is particularly valuable in large breeding units or when pastures are shared by herds of different origins.
Vaccination of animals has become the rule in some countries where bovine dermatophytosis is a notifiable disease (Gudding and Lund 1995). Anti-dermatophyte vaccines have been developed against dermatophytosis in cattle, horses, and less frequently sheep, but they are not available worldwide (Chermette et al. 2008). Both inactivated and live- attenuated vaccines, monovalent or multivalent, have been developed against animal ringworm. Ribosomal fractions of T. verrucosum have demonstrated promising immunogenic properties in cattle (Elad and Segal 1995). Recombinant protein and DNA vaccines derived from the heat-shock protein hsp60 of T. mentagrophytes allowed to control the clinical course of ringworm in guinea pigs and cattle (Milan et al. 2004). Other studies in horses using an inactivated preparation containing conidia and hyphae of T. equinum with adjuvant demonstrated a 75-87% relative protection of vaccinated horses against an infective contact (Pier and Zancanella 1993). Live vaccine against dermatophytes has been developed in the former USSR. A particular strain of T. verrucosum (the LTF 130 strain, with abundant production of microconidia in culture) was selected because of a high immunogenicity and attenuated pathogenicity. LTF live vaccines are currently used or have been used for several years in different countries, especially in Europe and on other continents (Canada, Cuba, Kenya, or Mongolia). To obtain optimal results, the vaccination program must concern all the animals of the cattle herd; then only the young calves between 2 weeks and 4 months of age and the newly introduced cattle will be vaccinated. In countries that have achieved successful control and eradication of cattle ringworm, a mass and systematic vaccination of cattle were undertaken. Failure of immunoprophylaxis can be explained by the non-respect of vaccination procedures, the reintroduction of infected cattle, the development of dermatophytes different from T. verrucosum and lack of crossed immunity, and the absence of hygienic and disinfection measures in farms. A dramatic reduction of dermatophytosis incidence in cattle, an improvement of the quality of leather and skins, and a decrease in case number of human contaminations have been observed when vaccination is correctly applied (Chermette et al. 2008; Seebacher et al. 2008).To date, there is no vaccine (with high level of efficacy and safety) for companion animals exposed to M. canis infection (Moriello et al. 2017). The vaccine licensed for use in cats in the USA in 1994 provided disappointing results and is not commercialized anymore. Broad-spectrum dermatophyte vaccines (for instance, against T. mentagrophytes and M. canis) are currently available in some European countries. They have been used in different species including pet carnivores and fur animals.
3.13