An exploratory analysis of demography and movement patterns of dogs: New insights in the ecology of endemic Rocky Mountain-Spotted Fever in Mexicali, Mexico

Abstract

An outbreak of Rocky Mountain spotted fever (RMSF) transmitted by the brown dog tick (Rhipicephalus sanguineus sensu lato) has emerged as a major human and animal health concern in Mexicali, Mexico. Due to high rates of brown dog tick infestation, susceptibility, and association with humans, dogs serve as sentinels and have a key role in the ecology of RMSF. A cross-sectional household questionnaire study was conducted in six rural and urban locations to characterize dog ecology and demography in RMSF high-and low-risk areas of Mexicali. In addition, we tracked movement patterns of 16 dogs using a GPS data logger. Of 253 households, 73% owned dogs, and dog ownership tended to be higher in high-risk areas, with a mean dog:human ratio of 0.43, compared with 0.3 in low-risk areas. Dogs in high-risk areas had higher fecundity and roamed more, but the dog density and numbers of free-roaming dogs were comparable. There was a higher proportion of younger dogs and lower proportion of older dogs in high-risk areas. The high proportion of immunologically naïve puppies in high risk areas could result in a lack of herd immunity leading to a more vulnerable dog and human population. The marked increase of space use of freeroaming dogs in high-risk areas suggests that unrestrained dogs could play an important role in spreading ticks and pathogens. As means to limit RMSF risk, practical changes could include increased efforts for spay-neuter and policies encouraging dog restraint to limit canine roaming and spread of ticks across communities; due to dog density is less impactful such policies may be more useful than restrictions on the number of owned dogs.

Comparative Study of Free-Roaming Domestic Dog Management and Roaming Behavior Across Four Countries: Chad, Guatemala, Indonesia, and Uganda

“…Free-roaming domestic dog (FRDD) movements have been studied in various countries across the world. Previous studies involved dogs living in Australia (1)(2)(3)(4)(5)(6)(7)(8); Latin America, including Brazil (9, 10), Mexico (11,12), and Chile (13)(14)(15)(16); and Asia, including India (17), Tibet (18), and Kyrgyzstan (19). To the best of our knowledge, no study investigated FRDD roaming behavior in Africa so far.…”

“…To the best of our knowledge, no study investigated FRDD roaming behavior in Africa so far. Often, data were collected using Global Positioning System (GPS) tracking devices ( 1 – 4 , 6 – 8 , 11 – 16 , 18 – 20 ), but other tools, such as capture–recapture ( 10 , 21 ) or interviews ( 9 ), were also used to collect data on FRDD roaming behavior. Home range ( 2 , 14 , 17 , 19 ), the area a dog commonly uses for normal activities, such as breeding or foraging, and distance from home ( 12 , 13 , 20 ) were applied to describe and investigate dog roaming behavior.…”

“…FRDD play an important role in rabies spread since dogs are considered as the main source for rabies transmission to humans ( 24 ). However, dog behavior has also been investigated in regard to other dog-transmitted zoonotic diseases, such as echinococcosis ( 18 , 19 ), Leishmaniasis ( 25 , 26 ), or Rocky Mountain spotted fever ( 11 ), because of their impact on human health. The objectives of those studies include the refinement of current control strategies in endemic areas, preventing disease incursion in countries free from specific diseases (e.g., rabies in Australia) and informing dog population management programs ( 20 , 23 , 27 ).…”

“…Variability in the findings between these studies could be explained by differences in the study design, in the analytical methods, or by the influence of site-specific factors ( 11 ). Study design differences include type of data collected (georeferenced capture sites or GPS collar locations), data collection period [from hours ( 19 ) to months ( 3 )], or time interval between GPS fixes [from 15 s ( 5 ) to 30 min ( 1 )].…”

“…Study design differences include type of data collected (georeferenced capture sites or GPS collar locations), data collection period [from hours ( 19 ) to months ( 3 )], or time interval between GPS fixes [from 15 s ( 5 ) to 30 min ( 1 )]. Methodological differences can be found for home range size estimations, varying between minimum convex polygon (MCP) ( 6 , 11 , 13 , 14 , 18 ), the characteristic hull polygon ( 19 ), the time localized convex Hull (T-LoCoH) ( 16 ), the fixed kernel density distribution ( 1 ), and the biased random bridge method (BRB) ( 2 – 4 ). Dürr et al compared several methods including the MCP, fixed kernel density distribution, T-LoCoH, and BRB and concluded that the BRB was more suitable for FRDD home range size estimation as it considers tracks and not only locations collected by the GPS devices ( 2 ).…”