{"id":3451,"date":"2024-07-31T14:43:49","date_gmt":"2024-07-31T04:43:49","guid":{"rendered":"https:\/\/theveterinarian.com.au\/?p=3451"},"modified":"2024-08-14T15:06:11","modified_gmt":"2024-08-14T05:06:11","slug":"warm-wet-weather-creates-ideal-conditions-for-spread-of-toxocara-app-roundworms-and-other-canine-soil-transmitted-helminths","status":"publish","type":"post","link":"https:\/\/theveterinarian.com.au\/?p=3451","title":{"rendered":"Warm & Wet Weather Creates Ideal Conditions For Spread of Toxocara app. Roundworms and Other Canine Soil- Transmitted Helminths"},"content":{"rendered":"\n

Warm and wet weather creates ideal conditions for spread of <\/strong><\/p>\n\n\n\n

Toxocara spp. <\/em><\/strong>roundworms and other canine soil-transmitted helminths<\/strong><\/p>\n\n\n\n

Dog parks provide an ideal urban space where dogs and their owners can exercise, play and socialise in a safe environment. These parks can however also increase the risk of exposure to infectious and parasitic agents including canine soil-transmitted helminths which are endemic to Australia, such as roundworms, hookworms, whipworms and Strongyloides <\/em>spp. A recent study showed that almost half (42.6%) of all dog parks across Australia were contaminated with at least one species of canine soil-transmitted helminth, with on average more than 1 in 10 faecal samples (12.7%) testing positive.1<\/sup> Climate (higher average rainfall and temperature) and socioeconomic factors (lower socioeconomic indices score) were shown to be associated with a greater risk of contamination. A consideration of these parasites is important as they impact not only animal health and wellbeing but also potentially human health, with many also being zoonotic. <\/p>\n\n\n\n

Recent wet weather across the country and the forecast of an unusually warm winter by the Bureau of Meteorology may increase the risk of exposure of dogs and people to canine soil-transmitted helminths.\u00a0<\/strong>Worm larvae develop more quickly in warm and wet conditions and can survive for longer periods of time. Additionally, heavy rain can result in the spread of worm eggs and larvae across the park, rather than having them found in or immediately next to deposited faeces.<\/p>\n\n\n\n

Toxocariasis<\/strong><\/p>\n\n\n\n

Toxocariasis is an infection in humans caused by the larvae of\u00a0Toxocara<\/em>\u00a0spp. roundworms. It is a clinically significant zoonosis, yet it remains a persistent problem in dogs and cats worldwide despite readily available and effective anthelmintics. Three species of roundworm are known to infest dogs and cats:\u00a0Toxocara canis<\/em>\u00a0(canine only),\u00a0T. cati<\/em>(feline only) and\u00a0Toxascaris leonina<\/em>\u00a0(canine and feline).\u00a0Toxocara canis<\/em>\u00a0and\u00a0T. cati<\/em>\u00a0are the most clinically significant species due to their zoonotic potential and capacity to cause disease in dogs and cats.2<\/sup><\/p>\n\n\n\n

A major challenge in preventing zoonotic\u00a0Toxocara<\/em>\u00a0infections is the ability of roundworm eggs to survive for years in the environment. Human infections occur through the accidental ingestion of eggs from contaminated soil (gardens, sandpits and parks), or on unwashed hands, objects or raw vegetables.3,4<\/sup>\u00a0Studies from all over the world have demonstrated high rates (13-35%) of soil contamination with\u00a0Toxocara<\/em>\u00a0spp. eggs in public places such as sandpits, parks, playgrounds and beaches.5<\/sup>\u00a0These worms can also infect a range of other animals such as chickens and cattle and the ingestion of raw or undercooked meat is another potential source of transmission. While roundworm cannot complete maturation in humans, developing larvae can migrate through the body and result in signs of disease.\u00a0<\/p>\n\n\n

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Embryonated Toxocara canis egg<\/figcaption><\/figure><\/div>\n\n\n

In humans,\u00a0Toxocara<\/em>\u00a0larvae can penetrate the intestinal mucosa and migrate to the liver, lungs and other organ systems (e.g., skeletal muscle, heart, brain and eyes). Migrating larvae are attacked by host immune responses, resulting in local inflammation. A number of clinical syndromes are recognised as being caused by\u00a0Toxocara\u00a0<\/em>infection: visceral larva migrans, ocular larva migrans, covert or common toxocariasis, and neurotoxocariasis.6,7<\/sup>\u00a0In addition to more overt clinical manifestations, studies have also shown that infection with roundworm can be positively associated with asthma and epilepsy in children.6<\/sup>\u00a0Additionally, a recent, large national study in the United States reported a strong association between serologically confirmed infection with\u00a0Toxocara\u00a0<\/em>spp. and diminished cognitive function in children aged 6-16 years in the general population.8<\/sup>\u00a0This relationship was independent of factors such as socioeconomic status, ethnicity, gender and rural residence.\u00a0\u00a0There is also evidence linking infection with\u00a0Toxocara\u00a0<\/em>with neurodegenerative conditions in older individuals, including Parkinson\u2019s disease and dementia, although more rigorous studies are needed to fully understand the significance of these associations.6<\/sup><\/p>\n\n\n\n

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Ocular larva migrans presenting as unilateral leukocoria Picture: American Academy of Ophthalmology
\u00a0<\/figcaption><\/figure>\n\n\n\n

Whilst severe consequences of human toxocariasis such as blindness are fortunately rare, infection is likely common and is potentially linked to a growing body of evidence of clinical and subclinical effects. A recent meta-analysis of published data estimated that seven per cent of Australians are seropositive for Toxocara <\/em>antibodies, indicating current or prior infection.9<\/sup><\/p>\n\n\n\n

It is likely that community awareness of the zoonotic potential of Toxocara<\/em> is low. Knowledge of the risks can be a driving force for owner behaviour change and veterinarians play a crucial role in driving owner compliance for control measures such as regular anthelmintic treatment. The Australian Veterinary Association policy on the role of veterinarians in the management of zoonotic disease states, \u201cVeterinarians should have knowledge of common and locally endemic zoonoses and their clinical impact on both animals and humans, actively educating all clients in strategies to minimize the risk of infection<\/em>\u201d.10<\/sup> For Toxocara <\/em>roundworms, such strategies would include:<\/p>\n\n\n\n