Fig. 4.
Compartmental model structure. The Tamil Nadu canine population of ∼1.5 million dogs was stratified into owned and stray strata. Within the stray stratum, dogs were classified as neither sterilized nor vaccinated (SS), vaccinated but unsterilized (VS), sterilized and vaccinated males (MS), sterilized and vaccinated females (FS), or sterilized but immunologically susceptible females (XS), the result of vaccine failure. Sterilized but immunologically susceptible males are identical to dogs in the SS class. Owned dogs were classified as either susceptible (SO) or vaccinated (VO). Unvaccinated dogs can become infected with rabies, whereupon they enter a latent phase (E) and then, progress to infectious phase (I). Infectious dogs do not recover, because rabies is inevitably fatal. Humans (SH) become exposed to rabies (EH) through bites from an infectious dog. Vaccine-protected canine epidemiological states are blue, and all other canine states are green. Human epidemiological states are yellow. Solid arrows indicate the transition of individuals between compartments, and dashed arrows represent rabies transmission.