PREVENTION
7.1 Anticoccidial drugs
Exposure to coccidia is impossible to prevent, because they are ubiquitous in the environment and shed by most echidnas. Exposure is essential for the development of immunity in juvenile echidnas on emergence from the natal burrow and ongoing exposure to low levels may be necessary to maintain immunity in adult echidnas.
Longterm prophylactic use of anticoccidial drugs has led to resistance in Eimeria spp. in production animals (Lan et al. 2017) and is not recommended and is impractical for routine prevention in echidnas (Slapeta 2016; Spielman 2016). Their use is reserved for clinical cases or as prophylaxis in the face of risk factors (Table 30.1 and section 6). Intermittent dosing with toltrazuril in chickens and rabbits has been shown to prevent clinical disease while allowing for the development of immunity (Peeters and Geeroms 1986; Greif 2000) and may be considered in hand-reared echidnas when first exposed to coccidial oocysts (J Slapetapers. comm.).The goal of prevention is to reduce, not eliminate oocyst shedding, so treatment with less effective anticoccidial drugs is advised (e.g. toltrazuril). Serial monitoring of faecal oocysts is recommended in at-risk echidnas, as is opportunistic monitoring of the level of parasitaemia. For example, free-ranging echidnas recently admitted to care should have faecal screening at least weekly and if shedding intensity increases significantly a 2-d course of tol- trazuril is suggested. Toltrazuril has resulted in inappetence (A Wallace pers. comm.; see Chapter 29), which could be from poor palatability, a potential unexplained adverse drug reaction or as a result of coccidiosis.
Regular monitoring of long-term healthy echidnas in managed care is not necessary, because of the lack of correlation between shedding intensity and health status (Debenham et al.
2012; A Wallace pers. comm.; Taronga Zoo records).7.2 Substrate
Desiccation, heat and ultraviolet light theoretically reduce oocyst survival. Coarse river sand, often used in breeding enclosures, offers excellent drainage and should reduce oocyst retention. Oocysts are more likely to accumulate in soil substrate, which is more commonly used in echidna enclosures. Although coccidia are described as ubiquitous and are excreted in large numbers in echidna faeces (J Slapeta pers. comm.), Debenham et al. (2012) and Perth Zoo found none or only a small number of coccidial oocysts in substrate from healthy echidna enclosures or outbreak locations, including latrine areas. This is most likely a result of redistribution of oocysts within soil. Importantly, infection can occur with the ingestion of a very small number of infective oocysts (J Slapeta pers. comm.).
Although the numbers of oocysts are generally low, it is recommended to remove the top layer of soil annually, in particular from the latrine area (J Slapeta pers. comm.). Disinfection is futile, as oocysts are extremely resistant, surviving bleach and 2% sulfuric acid under laboratory conditions (Slapeta 2016). Annual replacement or partial replacement of river sand substrate in breeding enclosures is recommended (M Pyne pers. comm.), in order to prevent exposure of emerging, non-immune echidnas to potential heavy environmental contamination (Debenham et al. 2012). However, exposure to low levels is important for development of immunity in juvenile echidnas which usually occurs from exposure to faeces from the dam.
7.3 Husbandry and minimising stressors
Optimal husbandry practices ensuring good hygiene, optimal nutrition and appropriate stocking densities are important. Faeces should be removed daily where possible, particularly when housed in small enclosures or for hospitalised individuals. Stressors such as noise, disturbance, frequent handling, pest species and incompatible enclosure cohabitants should be managed and minimised. Appropriate shelter and opportunities to thermoregulate in enclosures or when being transported are important. Sick echidnas must be isolated.
ACKNOWLEDGEMENTS
I thank Michael Pyne, Jan Slapeta, Simone Vitali and Alisa Wallace for the information they provided.