Agriculture Reference
In-Depth Information
8. Prevention and control of zoonotic soil-transmitted helminth infections in
humans and companion animals
Contaminated soil is the most important route of transmission of zoonotic helminths to
humans. Environmental contamination is particularly relevant when public areas (parks,
playgrounds, beaches) are affected. Effective preventive measures include covering
sandboxes in public parks and playgrounds when not in use, allowing no dogs and cats on
bathing beaches, and controlling stray dog and cat populations.
In southeastern Brazil, Santarém et al. (2004) reported a significant decrease in the incidence
of LMC after replacement of soil in sandboxes and enclosure of playground areas with
fences. Also in southern Brazil, Cassenote et al. (2011) observed that the frequency of geo-
helminthes in fenced parks (11.1%) was significantly lower than that verified in non-fenced
off areas (45.3). Similarly, Avcioglu & Balkaya (2011) observed in Turkey that fenced parks
were free of
Toxocara
eggs, while 64.3% of open areas were contaminated with eggs.
Periodic prophylactic deworming of companion animals and educational measures aimed at
pet owners are also critical for controlling infections by soil-transmitted helminths (Stull et
al., 2007). A strategic program for decreasing soil contamination with zoonotic helminths
should include elimination of intestinal parasites from puppies and kittens. Since puppies
and kittens harbor adult
Toxocara
and hookworm due to infections via placenta and/or milk,
treatment must target newborn animals, before eggs are first shed in the feces.
The WHO (2011), based on considerations by Barriga (1988, 1991), currently recommends
treatment for puppies at two weeks of age to eliminate larvae acquired through
transmammary or transplacentary transmission. Treatment is repeated at 4, 6 and 8 weeks.
For kittens, treatment must be done at third, fifth, seventh and ninth weeks of life to
eliminate the larva passed through milk. A single dose of anthelmintic for queens, 10 days
after delivery, is also recommended (Barriga, 1991). Laboratory confirmation of infection,
with stool examination using concentration methods (most often based on flotation
procedures), is normally required prior to treatment of animals older than six months of age,
to prevent uncontrolled use of anthelminthic drugs and the emergence of resistant parasites.
Veterinarians are thought to be on the 'front line' of prevention of pet-associated zoonotic
parasitic infections (Smith et al., 2009). However, recent surveys have revealed that
veterinarians often misinterpret and misuse the available protocols for deworming newborn
pets. In Canada, 80-90% of the protocols recommended for puppies and kittens were
inappropriate (Stull et al., 2007), and in the USA only 16% of the veterinarians interviewed
knew how to deworm puppies (Harvey et al., 1991). In addition, veterinarians' perception
concerning small animal-derived zoonoses should be improved, with emphasis on their role in
disseminating information about these diseases to their clients (Stull et al., 2007).
Human infections with canine and feline helminths ranks among the most common
zoonotic infections worldwide, yet remain relatively unknown to the public and pet owners.
Katagiri & Oliveira-Siqueira (2008), in São Paulo, Brazil, observed a low level of risk
perception of zoonotic infection by dog owners in Brazil. Pet owners should know how to
prevent environmental contamination and to reduce the risk of human infection with
zoonotic helminths. This requires a clear understanding of zoonoses acquired from small
animals, of the need for appropriate deworming strategies for pets, and the need for
removing feces from the environment where their dogs evacuate.
The public must also be informed about the risks of exposing children to public parks and
beaches frequented by animals and of eating soil or biting nails, as well as about the benefits
of washing hands after handling fecal material or playing with pets.
