Did disease constrain the spread of domestic dogs (Canis familiaris) into Sub-Saharan Africa?

Why the Donkey Did Not Go South: Disease as a Constraint on the Spread of Equus asinus into Southern Africa

“…Three such taxa survive today: Grévy's zebra (E. grevyi) in the semi-arid grasslands of Ethiopia and northern Kenya; the plains zebra (E. quagga) from Kenya south into South Africa; and the mountain zebra (E. zebra) in the Western and Eastern Cape Provinces of South Africa and in Namibia. As in the analogous cases of cattle (GiffordGonzalez 2000) and dogs (Mitchell 2015), when domesticated equids entered areas south of the Sahara and the Horn to which they were strangers they may have encountered pathogens to which they had no prior experience. The susceptibility of domestic horses to diseases originally restricted to Africa south of the Sahara is well established, and trypanosomiasis and African horse sickness, in particular, severely constrained their expansion south of the Sahel and in South Africa (Clutton-Brock 2000, pp.…”

“…Earlier research that explored the possible roles of infectious diseases in constraining the spread within Sub-Saharan Africa of both cattle (GiffordGonzalez 2000(GiffordGonzalez , 2016 and dogs (Mitchell 2015) suggests that this may be a productive line of enquiry for explaining why donkeys did not expand into southern Africa in precolonial times. Indeed, Blench (2000, p. 350) noted some time ago that in recent times Bthe clearing of savanna forest of the Sahel and the consequent decline in tsetse challenge has permitted donkeys to spread southwards^in West Africa [emphasis added].…”

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

“…This widespread late Pleistocene/early Holocene distribution is not, however, matched south of 20°N. Instead, from Central and South America to sub-Saharan Africa to Southeast Asia (including southern China and Indochina) and Australasia, the archaeological records of four continents struggle to identify the dog beyond 5000 years ago (Larson et al 2012;Mitchell 2015;Piper 2017;Stahl 2012). Indeed, in some regions, notably Africa south of the Equator or-as we shall see-much of South America, dogs first appeared much more recently than that.…”

“…Encouraged by the strength of Gifford-Gonzalez's arguments with respect to the relatively slow, late, and partial expansion of livestock into eastern and southern Africa, I have suggested that disease may also have constrained the spread of the domestic dog into the tropics (Mitchell 2015). The basis of this argument lies in the recognition that the dog's wild ancestor, the grey wolf, is not a tropical animal and that when they entered the tropics dogs probably therefore encountered a range of parasites with which they had no prior familiarity.…”

“…At least five infections seem relevant as potential constraints on the expansion of the dog south of the Sahara: canine trypanosomiasis, canine babesiosis, canine monocytic ehrlichiosis, visceral leishmaniasis and, possibly, African horse sickness (Mitchell 2015(Mitchell , 2017. All save leishmaniasis present severe disease challenges to dogs in Africa today.…”