The problem of stray dogs

The effective management of stray dogs is critically important in any rabies vaccination programme. In many rabies-endemic countries, stray dogs represent a significant proportion of both the free-roaming and total dog populations, and to ensure that rabies elimination programmes are successful, it is essential that this portion of the dog population (stray dogs) is vaccinated at high coverage. However, there are a number of challenges to managing and delivering rabies vaccinations to stray dogs. This paper will review the most pertinent issues relating to the problem of stray dogs and rabies elimination, focusing on the challenges relating to the estimation of population size, vaccination administration and vaccine coverage assessment in stray dog populations. The authors will highlight how these challenges can be overcome, notably by reviewing the census techniques that have been employed to assess stray dog populations, which then facilitate the planning and design of vaccination programmes. In addition, they discuss the range of vaccination strategies that are available and that have been used to vaccinate stray dogs and review how vaccination coverage can be assessed in this population. Finally, the benefits of population management in stray dogs through neutering programmes are reviewed. In short, this paper highlights the importance of ensuring that stray dogs, as well as owned dogs, are included in vaccination programmes and emphasises that many of the challenges related to protecting stray dogs from rabies can be overcome.

Evaluation of methods for short-term marking of domestic dogs for rabies control

Rabies transmitted by domestic dogs is a serious yet neglected public health threat in many underserved communities in Africa and Asia. Achieving 70% vaccination coverage in dog populations through annual mass vaccination campaigns is an effective means of controlling the disease in these communities. Evaluating the extent to which this target coverage is achieved requires either accurate pre-campaign estimates of the dog population size or accurate estimates of the coverage attained by conducting post-vaccination surveys. Short-term marking of dogs by applying visible marks may be useful to achieve these estimates, but will be affected by the performance of the marking methods. We evaluated the longevity and visibility of two readily-available livestock marking methods applied to owned, free roaming dogs. We applied two types of marks (spray and crayon) with three different colours (red, blue and green) to each of 21 dogs and compared the time of persistence of the marks over several weeks. Two independent observers assessed the visibility and colour of the marks. Each dog was observed over 8-37 days (median: 28 days). Kaplan-Meier survival analyses and semi-parametric log-rank tests were performed separately for both observers. Spray marks remained visible significantly longer (median of 24 days for both observers) compared with crayon marks (medians of 10 and 13 days). After 10 days, 90% of spray marks were still visible, compared with only 46% of crayon marks. Visibility of marks was reduced in darker-coloured dogs. Colours of marks were frequently misclassified, and agreement between observers on the colours of the marks was low (Cohen's kappa coefficient=0.27). The livestock marker spray can effectively be used to mark dogs that are physically restrained, for example during vaccination campaigns. Resight surveys should be conducted within a short a time as possible after marking; however, our results suggest that loss of marks will not have a significant impact if surveys are conducted within 5-7 days after marking with the spray. Results that depend on observers' abilities to distinguish between the three colours which we evaluated may not be reliable.

Changes in blood testosterone concentrations after surgical and chemical sterilization of male free-roaming dogs in southern Chile

There is a growing interest in chemical sterilization as an alternative to surgical castration in large-scale sterilization campaigns to control canine populations. An important step toward understanding the short-term and long-term effects of chemical sterilants is to determine their impact on blood testosterone concentrations, particularly as these could influence dog behavior after treatment. A field trial was conducted with 118 free-roaming male dogs in the Chilean Patagonia, where 36 dogs were chemically sterilized using EsterilSol, 39 dogs were surgically castrated, and 43 dogs remained intact as controls. Blood testosterone levels were determined at four time periods: on enrollment 6 months before treatment (t-6m), at the time of treatment (t0, within one hour after surgical castration or chemical sterilization and during a concurrent 2-week period for the control group), four (t+4m), and six (t+6m) months after treatment. Intrinsic and temporal factors were evaluated; age was significantly associated with testosterone, where dogs 2- to 4-year-old had the highest testosterone concentrations (P = 0.036), whereas body weight and body condition scores were not associated with testosterone; testosterone concentration was not influenced by time of day, month, or season. After treatment (t+4m and t+6m), all of the surgically castrated dogs had testosterone concentrations below 1.0 ng/mL. On the basis of this cut point (<1 ng/mL), testosterone remained unchanged in 66% of the chemically sterilized dogs at both t+4m and t+6m; it remained low for 22% of dogs at both t+4m and t+6m; it was unchanged at t+4m but low at t+6m in 9% of dogs; and, it was low at t+4m but reverted back to unchanged at t+6m in one dog (3%). Incidentally, testosterone in chemically sterilized dogs increased dramatically within 1 hour of treatment (t0), more than doubling (131%) the concentration of control dogs at the time of treatment (t0), likely because of severe necrosis of interstitial cells. The use of EsterilSol as a method of sterilizing dogs had a variable effect on blood testosterone concentrations. Approximately, 30% of chemically sterilized dogs had a reduced testosterone concentration (actual maximum, 1 ng/mL) after 6 months, similar to that of surgically castrated dogs. Most chemically sterilized dogs, however, showed no long-term changes in blood testosterone concentrations.