Disease: A Hitherto Unexplored Constraint on the Spread of Dogs (Canis lupus familiaris) in Pre-Columbian South America

Although debate continues, there is agreement that dogs (Canis lupus familiaris) were first domesticated in Eurasia, spreading from there to other parts of the world. However, while that expansion already extended as far as Europe, China, and North America by the early Holocene, dogs spread into (and south of) the tropics only much later. In South America, for example, the earliest well attested instances of their presence do not reach back much beyond 3000 cal. BC, and dogs were still absent from large parts of the continent – Amazonia, the Gran Chaco, and much of the Southern Cone – at European contact. Previous explanations for these patterns have focused on cultural choice, the unsuitability of dogs for hunting certain kinds of tropical forest prey, and otherwise unspecified environmental hazards, while acknowledging that Neotropical lowland forests witness high rates of canine mortality. Building on previous work in Sub-Saharan Africa (Mitchell 2015) and noting that the dog’s closest relatives, the grey wolf (C. lupus) and the coyote (C. latrans), were likewise absent from South and most of Central America in Pre- Columbian times, this paper explores instead the possibility that infectious disease constrained the spread of dogs into Neotropical environments. Four diseases are considered, all likely to be native and/or endemic to South America: canine distemper, canine trypanosomiasis, canine rangeliosis, and canine visceral leishmaniasis caused by infection with Leishmania amazonensis and L. colombiensis. The paper concludes by suggesting ways in which the hypothesis that disease constrained the expansion of dogs into South America can be developed further

Rangelia vitalii: changes in the enzymes ALT, CK and AST during the acute phase of experimental infection in dogs Rangelia vitalii: mudanças nas enzimas ALT, CK e AST na fase aguda da infecção experimental em cães

Rangelia vitalii is a protozoon that causes diseases in dogs, and anemia is the most common laboratory finding. However, few studies on the biochemical changes in dogs infected with this protozoon exist. Thus, this study aimed to investigate the biochemical changes in dogs experimentally infected with R. vitalii, during the acute phase of the infection. For this study, 12 female dogs (aged 6-12 months and weighing between 4 and 7 kg) were used, divided in two groups. Group A was composed of healthy dogs (n = 5); and group B consisted of infected animals (n = 7). Blood samples were collected on days 0, 10, 20 and 30 after infection, using tubes without anticoagulant to obtain serum and analyze the biochemical parameters. An increase in alanine aminotransferase (ALT) on day 20 (P < 0.05) was observed. Also, increased creatine kinase (CK) and aspartate aminotransferase (AST) levels were observed throughout the experimental period (P < 0.05). No changes in the serum gamma-glutamyltransferase, urea and creatinine levels were observed. Thus, is possible to conclude that experimental infection with R. vitalii in dogs causes changes to the biochemical profile, with increased ALT, AST and CK enzyme levels.<br>Rangelia vitalii é um protozoário que causa doença em cães, sendo a anemia o achado laboratorial mais frequente. No entanto, existem poucos estudos sobre as alterações bioquímicas em cães infectados com o protozoário. Assim, este estudo tem como objetivo investigar as alterações bioquímicas de cães experimentalmente infectados com R. vitalii na fase aguda da infecção. Para o estudo, foram utilizados 12 cães fêmeas (com idade entre 6 a 12 meses e peso entre 4 a 7 kg), divididos em dois grupos. O grupo A (n = 5) foi composto de animais saudáveis e o grupo B (n = 7) de animais infectados. Amostras de sangue foram coletadas nos dias zero, dez, vinte e trinta PI, utilizando tubos sem anticoagulante para obtenção de soro e análise dos parâmetros bioquímicos. Foi observado um aumento na alanino aminotransferase (ALT) no dia 20 PI (P < 0,05) e aumento na creatinoquinase (CK) e aspartato aminotransferase (AST) em todo o período experimental (P < 0,05). Não foram observadas alterações séricas na gama-glutamiltransferase, uréia e creatinina. Portanto, é possível concluir que a infecção experimental por R. vitalii causa alterações no perfil bioquímico, com aumento na ALT, CK e AST