Domesticated dogs, genomes, and malaria

Plasmodium falciparum is a unicelluar protozoan parasite of humans and the deadliest species of Plasmodium. It is transmitted through the bite of a female Anopheles mosquito and responsible for Therefore it is regarded as the deadliest parasite in humans, causing at least one million deaths every year. The species evolved about 10,000 years ago from the malarial parasite found in gorillas. A World Health Organization report in 2015, suggested there were 214 million cases of malaria worldwide.

Dogs spread across the globe with humans and have had to adapt to the same environmental conditions as humans. A Chinese research team led by Zhang has successfully identified genes selected in African dogs and functionally verified the action of one of these as the first evidence of dog adaptation to malaria.

“Recently, we have shown the first evidence that dogs can undergo similar adaptations as humans, using the same genes to live in the high altitudes of Tibet,” said professor Ya-Ping Zhang.

“Dogs have survived in tropical environments for thousands of years alongside humans,” said Zhang. “In this study, we have identified genes associated with insulin secretion and sensitivity, immunity, angiogenesis and ultraviolet protection showed adaptive selection.”

Yan-Hu Liu et al. (2017) sequenced the genomes of 19 dogs from Nigeria. For this new data set, they identified a set of candidate genes for natural selection in African village dogs and also carried out functional studies to confirm that one of these, ADGRE1, might be responsible for providing host immunity to Plasmodium infection—a target of selection associated with malaria.

“Our study suggests ADGRE1 also contributes to defense against Plasmodium infection in dogs, and thus, convergent evolution in this gene between humans and dogs,” said Guo-Dong Wang. “This is a novel finding since in earlier studies the most apparent cases of convergent evolution between humans and dogs were in genes for digestion and metabolism, neurological process, and cancer.”

The authors went on to show in cell culture experiments in the lab that the derived variant of ADGRE1 is linked to increased phagocytosis in cells infected with Plasmodium parasites, making it very likely that the ADGRE1 confers protection against Plasmodium infection by stimulating the immune response against the parasite.

In addition, they investigated the Nigerian dogs’ demographic history in relation to other dogs, including Eurasian gray wolves and African golden wolves. They found that the Nigerian dog population diverged from Eurasian dog populations around 14,000 years ago. After this divergence, the population fell on hard times, and experienced a severe bottleneck (leading to a reduced genetic diversity within the Nigerian dog population) and also gene flow from African golden wolves after the divergence.

Finally, they explored signals of selection in the Nigerian dog samples, and identified a number of candidate genes that are also linked to dietary and environmental factors.

As the authors note, since ADGRE1 has also been implicated in an adaptive response to Plasmodium in humans, it makes for a nice genetic tale of dogs utilizing similar tricks from living alongside their human companions to adapt to new environments.

References

Caspermeyer J. 2017. Scientists Find Evidence Our Best Friends, Dogs, Similarly Adapted to Malaria in Africa, Molecular Biology and Evolution,  msx289, https://doi.org/10.1093/molbev/msx289

Liu Y-H, Wang L, Xu T, Guo X, Li Y, Yin T-T, Yang H-C, Yang H, Adeola AC, Sanke OJ, et al. 2017. Whole-genome sequencing of African dogs provides insights into adaptations against tropical parasites. Molecular Biology and Evolution.

 Advance Access published October 10, 2017, doi: 10.1093/molbev/msx258

Wolf parasites in domestic dogs

Grey wolves, like all wild animals, are hosts to a variety of parasites. The presence of grey wolves in German forests has little influence on the parasite burden of hunting dogs. This reassuring conclusion is the result of a new study at the Berlin-based Leibniz Institute for Zoo and Wildlife Research (IZW). The study examined the feces of 78 hunting dogs over several months in an area without wolves and in one that had been recolonized. The results have been published in the open access scientific journal International Journal for Parasitology: Parasites and Wildlife.

Since the early 1990s grey wolves are expanding their range in central Europe. This recolonization gives rise to many questions about this apex predator and its influence on the environment and the life cycles of its parasites, prey, and potential competitors. Scientists at the Leibniz-IZW have now uncovered that the presence of wolves has little impact on the parasite burden of domestic dogs used for hunting prey of wolves. The scientists compared hunting dogs based in Eastern Germany, where wolves have re-established themselves since early 2000, with hunting dogs in North of Germany, where -- at the time of the study -- there were no resident wolf packs.

Grey wolves in the Bavarian forest.Photo Credit: © gallas / Fotolia

"Hunting dogs, unlike companion dogs, are especially well suited for this comparison as they, just like the wolf, rummage through forests and have access to game meat.," Ines Lesniak, a scientist at Leibniz-IZW, explains. "The study focused on the parasites of the internal organs, so-called endoparasites, which can be identified in the feces of the host." In a previous study, the spectrum of endoparasites present in German grey wolves was described. As previously, the researchers used genetic techniques to determine the presence of parasitic worms and protozoan intestinal parasites belonging to the Sarcocystis genus in hunting dogs. Both the rate of infection and the species richness of worms and Sarcocystis species found in the dogs did not differ between the study areas with and without wolves. The parasite spectrum of hunting dogs and wolves overlapped considerably, indicating that dogs might have replaced the wolf during its absence as an alternate and suitable definite host in the life cycles of some parasites. A single Sarcocystis species (Sarcocystis grueneri), previously identified as a "wolf specialist," was discovered more frequently in hunting dogs in wolf areas than in hunting dogs in areas without wolves. Like many tapeworms, these protozoans have a life cycle in which carnivores, like dogs or wolves, function as definite host and their prey, such as roe deer and red deer, act as intermediate hosts.

"Unlike wild animals, hunting dogs are regularly dewormed, including the individual hunting dogs which participated in our study," Lesniak emphasizes. "However, these medical treatments do not affect protozoan parasites such as Sarcocystis." The scientists suspect that the high infection probability of hunting dogs -- over 60 percent in both study areas -- is caused by the routine feeding of game meat or offal. "It's in the owner's hands," Lesniak says. "Many study participants already act very responsibly by deworming their dogs on a regular basis; in the best cases several times a year." The official recommendation of the European Scientific Council for Companion Animal Parasites (ESCCAP) is that there should be a monthly treatment of risk groups such as hunting dogs. Such a regular treatment prevents parasitic worms from reproduction in the host and subsequent egg development, which thereby improves the health and wellbeing of the hunting dog. "Dog owners can also reduce the parasite burden of their dogs by the careful feeding of meat leftovers. Cooking the meat is a simple precautionary measure that inactivates all parasites -- from protozoans to tapeworm cysts -- as well as other pathogens that might be present in the meat." The Leibniz-IZW considers wolves to play a minor role regarding the excretion and distribution of parasites. "The number of wolves in Germany is extremely low compared to other carnivores such as red foxes or raccoon dogs, which can also serve as hosts for these parasites, and it is also low in comparison to the number of hunting dogs," comments the senior author of the study, Dr. Oliver Krone.

German dog owners can rejoice: None of the parasite species found in hunting dogs are an unreasonable health risk to humans, irrespective of whether the dogs live in an area where wolves are present or not present. The regular treatment with anthelmintics and feeding of cooked leftovers are simple but effective measures to maintain the health of hunting dogs. The Leibniz-IZW study illustrates that concerns regarding pathogens related to the return of wolves are currently unjustified.


Citations
Ines Lesniak, Mathias Franz, Ilja Heckmann, Alex D. Greenwood, Heribert Hofer, Oliver Krone. Surrogate hosts: Hunting dogs and recolonizing grey wolves share their endoparasites. International Journal for Parasitology: Parasites and Wildlife, 2017; 6 (3): 278 DOI: 10.1016/j.ijppaw.2017.09.001

Ines Lesniak, Ilja Heckmann, Emanuel Heitlinger, Claudia A. Szentiks, Carsten Nowak, Verena Harms, Anne Jarausch, Ilka Reinhardt, Gesa Kluth, Heribert Hofer, Oliver Krone. Population expansion and individual age affect endoparasite richness and diversity in a recolonising large carnivore population. Scientific Reports, 2017; 7: 41730 DOI: 10.1038/srep41730

The Origin of Dingoes

Pure dingoes come in a variety of colors including ginger, black and tan,
white and sable. Credit: Lyn Watson/Australian Dingo Foundation

A major study of dingo DNA has revealed dingoes most likely migrated to Australia in two separate waves via a former land bridge with Papua New Guinea.

The find has significant implications for conservation, with researchers recommending the two genetically distinct populations of dingoes -- in the south-east and north-west of the country -- be treated as different groups for management and conservation purposes.

"Care should be taken not to move dingoes between the different wild populations," says study first author and UNSW Sydney scientist Dr. Kylie Cairns.

"And captive breeding programs should ensure the two dingo populations are maintained separately, with genetic testing used to identify ancestry."

Further, inter-breeding also needs to be urgently prevented between domestic dogs and the south-eastern population of dingoes, which is threatened by genetic dilution, habitat loss and lethal control measures such as baiting and the recently reintroduced wild dog bounty in Victoria.

"Effective containment or neutering of male dogs in rural areas may help achieve this reduction in inter-breeding," says Dr. Cairns, of the School of Biological, Earth and Environmental Sciences.

"Additionally, baiting and culling practices break apart dingo packs, leading to increased incidence of hybridization. Alternative livestock protection measures need to be explored, such as livestock guardians, predator deterrents, and improved dingo-proof fencing," she says.

The study, by scientists from UNSW and the University of California, is published in the journal Ecology and Evolution.

The study is the first broad study of the evolutionary history of dingoes around Australia using both mitochondrial and Y-chromosome genetic markers.

The researchers sampled 127 dingoes across Australia as well as five New Guinea Singing Dogs from a North American captive population. A dataset of Y chromosome and mitochondrial control region data from 173 male dogs, including 94 dingoes, was also used.

Only genetically pure dingoes were included in the study.

The north-western population is found in Western Australia, the Northern Territory, northern parts of South Australia, and central and northern Queensland.

The south-eastern population is found in New South Wales, the Australian Capital Territory, Victoria and southern parts of Queensland (including Fraser Island).

The researchers believe the two groups may have migrated separately from Papua New Guinea over the now-flooded land bridge as long as 8000 to 10,000 years ago.

Particularly in south-eastern states, they recommend a broad survey of dingoes in national parks and state forests be carried out to focus conservation efforts in key areas, and also that state and federal legislation allowing fatal control measures be reviewed.



Citation
Kylie M. Cairns, Sarah K. Brown, Benjamin N. Sacks, J. William O. Ballard. Conservation implications for dingoes from the maternal and paternal genome: Multiple populations, dog introgression, and demography. Ecology and Evolution, 2017; DOI: 10.1002/ece3.3487

Making a New Dog

On landscapes around the world, environmental change is bringing people and large carnivores together -- but the union is not without its problems. Human-wildlife conflict is on the rise as development continues unabated and apex predators begin to reoccupy their former ranges. Further complicating matters, many of these species are now reliant on anthropogenic, or human, foods, including livestock, livestock and other ungulate carcasses, and garbage.

Writing in BioScience, Thomas Newsome, of Deakin University and the University of Sydney, and his colleagues use gray wolves and other large predators as case studies to explore the effects of anthropogenic foods. They find numerous instances of species' changing their social structures, movements, and behavior to acquire human-provisioned resources. For instance, in central Iran, gray wolves' diets consist almost entirely of farmed chickens, domestic goats, and trash.

Other instances of these phenomena abound. In a similar case in Australia, dingoes gained access to anthropogenic foods from a waste facility. The result, according to the authors, was "decreased home-range areas and movements, larger group sizes, and altered dietary preferences to the extent that they filled a similar dietary niche to domestic dogs." Moreover, wrote the authors, "the population of subsidized dingoes was a genetically distinct cluster," which may portend future speciation events. Hybridization among similar predator species may also contribute to evolutionary divergence: "Anthropogenic resources in human-modified environments could increase the probability of non-aggressive contact" between species. According to the authors, "If extant wolves continue to increase their reliance on anthropogenic foods, we should expect to observe evidence of dietary niche differentiation and, over time, the development of genetic structure that could signal incipient speciation."

Wolves' use of anthropogenic food could have serious implications for wider conservation efforts, as well. In particular, Newsome and his colleagues raise concerns about whether wolf reintroduction and recolonisation programs will meet ecosystem-restoration goals in human-modified systems. Managers will need to consider "how broadly insights into the role played by wolves gleaned from protected areas such as Yellowstone can be applied in areas that have been greatly modified by humans," say the authors.

Newsome and his colleagues call for further research -- in particular, "studies showing the niche characteristics and population structure of wolves in areas where human influence is pervasive and heavy reliance on human foods has been documented." Through such studies, they argue that "we might be able to ask whether heavy reliance of anthropogenic subsidies can act as a driver of evolutionary divergence and, potentially, provide the makings of a new dog."

Citation
Thomas M. Newsome, Peter J. S. Fleming, Christopher R. Dickman, Tim S. Doherty, William J. Ripple, Euan G. Ritchie, Aaron J. Wirsing. Making a New Dog? BioScience, 2017; 67 (4): 374 DOI: 10.1093/biosci/bix022

Dogs demonstrate perspective

Humans are able to interpret the behavior of others by attributing mental states to them (and to themselves). By adopting the perspectives of other persons, they can assume their emotions, needs, and intentions and react accordingly. In the animal kingdom, the ability to attribute mental states (Theory of Mind) is a highly contentious issue. Cognitive biologists from the Messerli Research Institute of the University of Veterinary Medicine Vienna could prove with a new test procedure that dogs are not only able to identify whether a human has an eye for a food source and, therefore, knows where the food has been hidden. They can also apply this knowledge in order to correctly interpret cues by humans and find food they cannot see themselves. This perspective-taking ability is an important component of social intelligence. It helps dogs to cope with the human environment. The results have been published in the journal Animal Cognition.

The so-called Theory of Mind describes the ability in humans to understand mental states in conspecifics such as emotions, intentions, knowledge, beliefs and desires. This ability develops in humans within the first four or five years of life while it is usually denied in animals. Indications that animals can understand mental states or even states of knowledge of others have only been found in apes and corvids so far. Dogs have been tested several times, but the results were poor and contradictory.

With a new experimental approach, cognitive biologists from the Messerli Research Institute could now provide solid evidence for dogs being able to adopt our perspective. By adopting the position of a human and following their gaze, dogs understand what the human could see and, consequently, know. This ability to ascribe knowledge is only a component of a full-blown Theory of Mind, but an important one.

Identifying the right informant

The so-called Guesser-Knower paradigm is a standard test in research into the attribution of knowledge to others. This experiment involves two persons: a "Knower" who hides food, invisibly for the dog, in one of several food containers or knows where somebody else has hidden it, and a "Guesser." The Guesser has either not been in the room or covered her eyes during the hiding of the food. A non-transparent wall blocks the animals' view of the food being hidden. After that, the two humans become informants by pointing to different food containers.

The Knower always points to the baited container and the Guesser to another one. All containers smell of food. "To get the food, the dogs have to understand who knows the hiding place (Knower) and who does not and can, therefore, only guess (Guesser). They must identify the informant they can rely on if they have to decide for one food container," said principal investigator Ludwig Huber. In approximately 70 percent of the cases, the dogs chose the container indicated by the Knower - and thus were able to successfully accomplish the test. This result was independent of the position of the food container, the person acting as the Knower and where the Guesser was looking.

Dogs can adopt human perspectives

The only aim of this test series, however, was to independently confirm a study carried out in New Zealand. Clear evidence of dogs being able to adopt our perspective and take advantage of it was provided in a new test developed by the team, the so-called "Guesser looking away" test.

In this new experiment, a third person in the middle hides the food. This person does not give cues later on. The potential informants were kneeing left and right of this hider and looked to the same side and slightly down. Thus, one of the two persons looked towards the baiter, the other person looked away. "This means that the tested dogs, in order to get the food, had to judge who is the Knower by adopting the informants' perspectives and following their gazes," explained Huber. Even in this test, which is very difficult for the animals, approximately 70 percent of the trials had been mastered.

Adopting the human perspective leads to invisible food

Being able to adopt the perspective of a human does, however, not require the ability to understand intentions or wishes. "But the study showed that dogs can find out what humans or conspecifics can or cannot see," explained Huber. "By adopting the positions of humans and following their gazes geometrically, they find out what humans see and, therefore, know - and consequently whom they can trust or not."

In similar experiments, chimpanzees and few bird species such as scrub jays and ravens were able to understand the state of knowledge and also the intentions of conspecifics and modify their own behavior accordingly. For dogs, there have only been speculations and vague indications so far. But dogs understand our behavior very well, for example, our degree of attention. They can learn from directly visible cues such as gestures or gazes. Thus, they are able to find food even if their view of it has been blocked. "The ability to interpret our behavior and anticipate our intentions, which has obviously developed through a combination of domestication and individual experience, seems to have supported the ability to adopt our perspective," said Huber. "It still remains unclear which cognitive mechanisms contribute to this ability. But it helps dogs to find their way in our world very well."


Citation
Amélie Catala, Britta Mang, Lisa Wallis, Ludwig Huber. Dogs demonstrate perspective taking based on geometrical gaze following in a Guesser–Knower task. Animal Cognition, 2017; DOI: 10.1007/s10071-017-1082-x