Dogs can transmit dwarf threadworm infections to humans
Dogs are generally considered to be man's best friend and often live closely with their owners. Pathogens can easily pass from the four-legged friends to humans. According to a recent study, this also applies to the dwarf nematode Strongyloides stercoralis, whose infections can be dangerous, especially for people with a weakened immune system.
Scientists from the Max Planck Institute for Developmental Biology in Tübingen, in collaboration with colleagues from the Swiss Tropical and Public Health Institute in Basel and the Cambodian Ministry of Health, investigated the dwarf threadworm infections in dogs and humans. The molecular biological analysis of the dwarf nematode Strongyloides stercoralis showed that the pathogens can be transmitted between humans and dogs. The researchers published their study results in the specialist journal “PLOS Neglected Diseases”.
300 million people infected worldwide
The roundworm infections caused by roundworms are on the WHO list of neglected tropical diseases, according to the researchers. The dwarf worm Strongyloides stercoralis is particularly common in warm, humid regions of the world and affects both humans and animals. The researchers estimate that around 300 million people worldwide are infected with dwarf threadworms. The result is a so-called strongyloid base, which can be particularly dangerous for people with a weakened immune system, for example after an organ transplant or with immune system diseases.
Humans and pets share their parasites
According to the researchers, humans and dogs certainly share their parasites, but it has so far remained open whether the dwarf threadworm infections can also be assessed as such a zoonosis. Not least because the different pathogens of the species are so similar that they can only be distinguished from one another by genetic analysis. In their current study, the researchers therefore used a genetic analysis of this kind to investigate "whether humans and dogs in Cambodia are infected with the same species of the dwarf threadworm Strongyloides stercoralis or whether they are separate host-specific populations."
Genetic analysis of dwarf threadworms
According to the scientists, the close coexistence of humans and dogs in the rural areas of Cambodia, in combination with the high level of Strongyloides, was particularly suitable for determining whether "the dwarf threadworms found in dogs are genetically identical to those of their owners." The researchers isolated worms from dog faeces and human stool samples and compared the specimens found using nuclear and mitochondrial DNA for sequence polymorphisms, according to the Max Planck Institute.
Pygmy worm infections are a zoonosis
In dogs, the researchers were able to detect two different worm populations that are genetically clearly separated from one another. The larger populations were only found in dogs, while the second Strongyloides population was genetically identical to the type of pathogen found in humans. Accordingly, the dwarf nematode infection is to be classified as a zoonosis. "The results of the current study show that because of the overlapping populations, dogs have to be considered as a reservoir and thus a source of infection for human Strongyloides infections," reports the Max Planck Institute. This knowledge is important for combating Strongyloides infections in humans.