Toxocara canis larvae viability after disinfectant-exposition

Synergistic effects of using sodium hypochlorite (bleach) and desiccation in surface inactivation for Toxocara spp

Toxocara cati and T. canis are parasitic nematodes found in the intestines of cats and dogs respectively, with a cosmopolitan distribution, and the potential for anthropozoonotic transmission, resulting in human toxocariasis. Spread of Toxocara spp. is primarily through the ingestion of embryonated eggs contaminating surfaces or uncooked food, or through the ingestion of a paratenic host containing a third-stage larva. The Toxocara spp. eggshell is composed of a lipid layer providing a permeability barrier, a chitinous layer providing structural strength, and thin vitelline and uterine layers, which combined create a biologically resistant structure, making the Toxocara spp. egg very hardy, and capable of surviving for years in the natural environment. The use of sodium hypochlorite, household bleach, as a disinfectant for Toxocara spp. eggs has been reported, with results varying from ineffective to limited effectiveness depending on parameters including contact time, concentration, and temperature. Desiccation or humidity levels have also been reported to have an impact on larval development and/or survival of Toxocara spp. eggs. However, to date, after a thorough search of the literature, no relevant publications have been found that evaluated the use of sodium hypochlorite and desiccation in combination. These experiments aim to assess the effects of using a combination of desiccation and 10% bleach solution (0.6% sodium hypochlorite) on fertilized or embryonated eggs of T. cati, T. canis, and T. vitulorum. Results of these experiments highlight the synergistic effects of desiccation and bleach, and demonstrate a relatively simple method for surface inactivation, resulting in a decrease in viability or destruction of T. cati, T. canis and T. vitulorum eggs. Implications for these findings may apply to larger scale elimination of ascarid eggs from both research, veterinary, and farming facilities to mitigate transmission.

Role of cats in human toxocarosis

Toxocara cati, the feline ascarid, is ubiquitous in domestic cats globally and is increasingly recognised as an important zoonotic species. In the definitive host, infections with the adult ascarid usually do not present any clinical signs; if clinical signs do appear, it is usually in kittens infected with T. cati, especially by the transmammary route. Diseases may include cachexia, a pot-bellied appearance, respiratory disorders, diarrhoea, vomiting, among other signs, and these may present as early as 3 weeks of age. However, infections with Toxocara spp. larvae in paratenic hosts (including humans and many other animals), can result in serious complications from the migration of larvae. Historically, there has been an assumption that Toxocara canis was the most likely cause of Toxocara spp.-related disease; while it is probably true that T. canis is responsible for the majority of infections, it is important that those caused by T. cati are accurately identified so that the contribution of this parasite to human disease can be established and then handled appropriately. Overall, the detection of infections in cats and the control of parasite stages in the environment are essential to minimise the infection risk to other animals or humans.

Efficacy of a chlorocresol-based disinfectant product on Toxocara canis eggs

Toxocara canis is a common parasite of dogs and can cause zoonotic toxocariasis in humans. As a part of control programs for this agent, optimized hygiene including chemical disinfection is considered essential in the prevention and control of zoonotic toxocariasis in humans. However, commonly used disinfectants at present mostly fail to inhibit the embryogenesis and viability of T. canis eggs. To this effect, the present study was designed to evaluate the effect of a chlorocresol-based disinfectant product Neopredisan®135-1 (NP) on embryonic development of T. canis eggs in vitro and to investigate the infectivity of exposed eggs by assessing larval establishment in a mouse model. Under in vitro conditions, NP at a final concentration of 0.25, 0.50, 1, 2, or 4% all exhibited significant killing effect on T. canis embryogenesis compared with the control eggs (P < 0.05), regardless of contact times (30, 60, 90, or 120 min). Such killing activity increased in a concentration- and time-dependent manner, with a maximum killing efficacy of 95.81% at 4% concentration and 120 min exposure time. Comparisons between low and high concentrations and between short and long contact times concluded that a protocol using the 1% concentration of NP with a 90-min contact could be the most suitable for practical application. Additionally, the lower larval recovery in mice inoculated with eggs treated by either 0.25 or 0.5% NP than that from their corresponding controls (P < 0.05) verified once again that NP had an adverse impact on the larval development of T. canis eggs even at a low concentration. To the best of our knowledge, this is the first study to report the effect of the chlorocresol-based disinfectant NP on the embryonation and larval development of T. canis eggs, and the results presented here would contribute to environmental clearance and control of toxocariasis by providing an alternative disinfectant resource. However, it is highlighted that the clearance of the novel and existing sources of infection including larvated eggs in places treated with NP is not guaranteed and therefore continuous monitoring and additional disinfection are still required.

Ovocidal action of glutaraldehyde and benzalkonium chloride mixture on Aonchotheca bovis (Nematoda, Capillariidae) embryogenesis

Deinvasion, aimed at elimination of environmental exogenic stages of invasion agents and avoidance of their invasion to host organism, occupies an important place in the complex of sanitary and prophylactic activities against animal helminthosis diseases. Application of glutaraldehyde and benzalkonium chloride at vital activity and embryogenesis of Aonchotheca bovis (Schnyder, 1906) obtained from nematode female gonads was investigated with different concentration and exposures. Two test-cultures were used in the experiment. The first culture contained non-invasive eggs of A. bovis, the second contained invasive ones, obtained by the laboratory culturing of gonadic eggs until mobile larva maturing. It was established that glutaraldehyde and benzalkonium chloride mixture has a deinvasive capacity against A. bovis eggs, parasitizing on sheep. Ovocidal efficiency indexes appeared higher with use of the test culture against the non-invasive capillaria eggs’ test-culture. So, the high level of ovocidal efficiency of glutaraldehyde and benzalkonium chloride mixture against non-invasive A. bovis eggs culture was established at the concentration of 0.5% and exposure of 10–60 min (93.6–100.0%), and against the invasive A. bovis egg culture – at the concentration of 0.5% and exposure of 30 and 60 min (90.3–94.6%) and 1.0% at all exposures (100.0%). Ovocidal activity of the examined mixture was accompanied by specific morphological changes of nematode eggs structure. Destruction of the egg envelope, embryo loosening and decay and its dissolution were observed. Such changes are proved by metric indexes of width and length of capillaria eggs, envelope thickness and cap length, indicating the violation of embryogenesis of A. bovis. Thus, glutaraldehyde and benzalkonium chloride mixture of 1.0% concentration is a promising deinvasive agent suitable for effective fight against and prophylaxis of sheep-breeding nematodosis.

Is routine disinfection efficient in preventing contamination with Toxocara canis eggs?

Toxocara canis (Werner, 1782) is a zoonotic nematode commonly parasitizing dogs worldwide with great public health importance as the aetiological agent of human toxocariasis. In this respect, the aim of this study was to evaluate the effect of six disinfectant products commonly used in kennels, veterinary clinics and as household cleaning products on the embryogenesis and viability of T. canis eggs. The composition of active ingredients in these commercial disinfectants was sodium hypochlorite (A); a mix of N-(3-aminopropyl)-N-dodecylpropan-1.3-diamine and didecyldimethylammonium chloride (B); sodium dichloroisocyanurate dehydrate (C); a mix of glutaraldehyde, quaternary ammonium compounds, benzyl-c12-18-alkyldimethyl and chlorides (D); a mix of 2-propanol, ethanol, benzalkonium chloride and glucoprotamin (E); a mix of pentapotassium bis (peroxymonosulphate) bis (sulphate), sodium C10-13-alkylbenzenesulphonate, malic acid, sulphamidic acid, sodium toluenesulphonate, dipotassium peroxodisulphate and dipentene (F). After dilution, the tested disinfectants had the maximal concentration recommended by the manufacturer in order to achieve a biocidal effect. Each product was tested on approximately 10,000 T. canis eggs, having five different contact times (5, 10, 15, 30, 60 min). Three replicates were tested for each diluted disinfectant and for each contact time. After the treatment, eggs were washed and incubated in distilled water at 27 °C for 2 weeks. None of the tested products had a significant inhibitory effect on the embryogenesis and viability of T. canis eggs, regardless of the contact time. Moreover, after 2 weeks, in all tested samples, eggs containing motile infective larvae were identified, showing that routinely used disinfectants do not eliminate risk of infection by T. canis.

Gastrointestinal Parasites in Shelter Dogs: Occurrence, Pathology, Treatment and Risk to Shelter Workers

Dogs entering shelters can carry gastrointestinal parasites that may pose serious risks to other animals, shelter staff and visitors. Shelters provide an environment that could facilitate the spread of parasitic infections between animals. Nematodes and protozoa that transmit through ingestion or skin penetration are major enteric parasites of concern in shelter settings. Ancylostoma spp., Uncinaria stenocephala, Toxocara canis, Toxascaris leonina, Trichuris vulpis and Dipylidium caninum are the major helminths while Giardia, Cryptosporidium, Isospora spp. and Sarcocystis spp. are the most prevalent protozoan parasites in shelter dogs. The prevalence of gastrointestinal parasites in shelter dogs is typically higher than in owned dogs. A range of cost-effective drugs is available for prevention and control of helminths in shelters, notably fenbendazole, pyrantel, oxantel, and praziquantel. Parasiticide options for protozoan parasites are often cost-prohibitive or limited by a lack of veterinary registration for use in dogs. Environmental control measures reliant upon hygiene and facility management are therefore a mainstay for control and prevention of protozoan parasites in shelters. This philosophy should also extend to helminth control, as integrated parasite control strategies can allow anthelmintics to be used more sparingly and judiciously. The purpose of this article is to comprehensively review the current knowledge on the prevalence of gastrointestinal parasites most commonly found in dogs in shelters, canvass recommended treatment programs in shelter dogs, and to explore the likelihood that parasiticide resistance might emerge in a shelter environment.

Developmental stages and viability of Toxocara canis eggs outside the host

Introducción. La toxocariasis es una enfermedad zoonótica transmitida por contacto con el suelo contaminado y causada principalmente por la ingestión de huevos larvados de Toxocara canis.Objetivos. Estudiar la morfología de los estadios intraovulares en desarrollo de T. canis en cultivo, caracterizar los huevos no viables y las secuencias de las mudas larvarias, y comparar la viabilidad de los huevos en las etapas tempranas de división y al alcanzar la maduración completa.Materiales y métodos. Se observó el desarrollo de los embriones y se caracterizaron los huevos no viables, mediante microscopía de luz. Se comparó la proporción de huevos viables con embrión con la de huevos maduros viables.Resultados. La división celular comenzó 24 horas después de iniciado el cultivo. Los estadios tempranos estuvieron presentes por un periodo de tres a cinco días. Los estadios de desarrollo identificados fueron: huevos con una célula, con dos células, con tres células y con cuatro células; mórula temprana, mórula tardía, blástula, gástrula, renacuajo, prelarva, primer, segundo y tercer estado larvario. Se presentaron dos mudas larvarias. Los huevos no viables tenían el citoplasma degradado, cubierta exterior delgada o colapsada, y su larva no se movía al exponerla a la luz. No se encontraron diferencias significativas entre la proporción de huevos viables del día 5 al día 21, al compararla con la viabilidad de los huevos completamente maduros (30 días).Conclusión. Los embriones en desarrollo en el medio ambiente pueden considerarse como un riesgo potencial para la salud pública. La identificación precisa de los estadios de desarrollo y la clara diferenciación de huevos viables y no viables, pueden ayudar a determinar con exactitud una tasa basal de desarrollo, la cual sería útil en el estudio de compuestos ovicidas.

In vitro study of disinfectants on the embryonation and survival of Toxascaris leonina eggs

The effect of six available and commercial disinfectants on the embryonation and larval development of Toxascaris leonina eggs was studied. Dettol® and Virkon® both induced a 100% reduction in larval development (P ≤ 0.05). Dettol® resulted in deformed eggshells and a halt in embryonal development at 1 week post exposure. All Virkon®-treated eggs showed an early embryonic lysis 24 h post exposure. TH4+ and 70% ethanol both significantly (P ≤ 0.05) affected larval development, with 58.8 and 85.8% reduction, respectively. Neither sodium hypochlorite nor phenol significantly affected larval development (2.8 and 21.0%, respectively). Sodium hypochlorite treatment caused a visible decortication of the eggshell; however, phenol-treated embryonated Toxascaris eggs appeared more or less morphologically normal. In conclusion, the disinfectants tested induced variable degrees of decortication and suppression of larval development. Virkon®S was the most effective disinfectant against Toxascaris eggs, suggesting that it is the most advisable one to use. To the best of our knowledge, this is the first report of the use of Virkon®S as an ovicide and/or larvicide of helminths, particularly Toxascaris leonina.

Effects of Disinfectants on Larval Development of Ascaris suum Eggs

The objective of this study was to evaluate the effects of several different commercial disinfectants on the embryogenic development of Ascaris suum eggs. A 1-ml aliquot of each disinfectant was mixed with approximately 40,000 decorticated or intact A. suum eggs in sterile tubes. After each treatment time (at 0.5, 1, 5, 10, 30, and 60 min), disinfectants were washed away, and egg suspensions were incubated at 25˚C in distilled water for development of larvae inside. At 3 weeks of incubation after exposure, ethanol, methanol, and chlorohexidin treatments did not affect the larval development of A. suum eggs, regardless of their concentration and treatment time. Among disinfectants tested in this study, 3% cresol, 0.2% sodium hypochlorite and 0.02% sodium hypochlorite delayed but not inactivated the embryonation of decorticated eggs at 3 weeks of incubation, because at 6 weeks of incubation, undeveloped eggs completed embryonation regardless of exposure time, except for 10% povidone iodine. When the albumin layer of A. suum eggs remained intact, however, even the 10% povidone iodine solution took at least 5 min to reasonably inactivate most eggs, but never completely kill them with even 60 min of exposure. This study demonstrated that the treatment of A. suum eggs with many commercially available disinfectants does not affect the embryonation. Although some disinfectants may delay or stop the embryonation of A. suum eggs, they can hardly kill them completely.

Temperature and the development and survival of infective Toxocara canis larvae

The influence of temperature on the development and survival of Toxocara canis larvae was investigated under laboratory conditions, in water at 15, 20, 25, 30 and 35°C and at room temperature 22°C ± 1°C. T. canis eggs were able to develop to the larvated stage at all the tested temperatures. Development rate increased with temperature. Linear regression of development rate against temperature predicted a lower development threshold of 11.8°C. Eggs survived cooling to 1 and -2°C for 6 weeks, and could develop to the infective, larvated stage when transferred to higher temperatures, but their development rates were then retarded compared with non-chilled eggs. Larvated eggs remained viable after 7 weeks of incubation across the tested temperature range, with the highest percentage viability (47%) obtained at 25°C. Development of eggs to the infective larval stage required, on average, 121 degree days between 20°C and 30°C. Results provide a basis for predicting variation in the infectivity of eggs in the environment over time in different climates.