Patent Toxocara canis infections in previously exposed and in helminth-free dogs after infection with low numbers of embryonated eggs

The outcome of Toxocara canis infections in the canine host depends on the migratory pathway of parasite larvae (somatic or tracheal) which is considered to be related to the host's age and its immune status. However, field studies attest high prevalences of patent T. canis infections in adult animals. The controlled induction of patent infections with low doses of embryonated eggs was investigated in 18 beagles in a 7-month study until their 16th life month. The animals were assigned to three groups, each consisting of three vertically infected dogs (with a short patent infection as pups before anthelmintic treatment) and three helminth-free dogs. At study days 10 and 40, the animals of groups 1 and 3 were given each 100 embryonated T. canis eggs. In each case, group 1 was treated 10 days post-infection with Milbemax, while dogs of group 3 remained untreated. Control group 2 was not experimentally infected but treated as group 1. Two weeks after first egg administration, a sharp increase of specific antibody reactions in ELISA and increased eosinophilic counts indicated larval invasion in all infected dogs. 42-56 days following first infection, patent infections were detected coproscopically in all animals of group 3, but in none of the uninfected dogs (group 2) or the infected and treated dogs (group 1). Following a 3-month observation period, all animals of the three groups were treated with piperazine citrate to eliminate intestinal infections and all were administered 100 embryonated eggs. Subsequently, patent infections developed in animals of all groups: in one of the infected and treated animals of group 1, in five of the so far not infected control group 2 and in four of the dogs with previous patent infections (group 3). Susceptibility to patent infections was not significantly altered in T. canis-free dogs compared to dogs with previous patent infection (vertically acquired or experimentally induced). However, dogs of group 1 treated with Milbemax after repeated egg administration developed a significantly increased resistance to patent infections as compared to control dogs (group 2). Observed prepatency periods were between 40 and 56 days and did not differ in the three groups. Even in urban areas, facing high infection pressure with Toxocara eggs maintained by a high dog and fox population, dogs of all ages are at risk to develop patent T. canis infections.     

An estimation of Toxocara canis prevalence in dogs,environmental egg contamination and risk of human infection in the Marche region of Italy

The human risk of infection with larvae of Toxocara canis was estimated in people from the Marche region of Italy. This region includes both urban and rural areas and its inhabitants frequently keep dogs for company, hunting, as guardians or shepherds. T. canis infection was diagnosed in 33.6% out of 295 dogs examined. Nearly half of the dogs (48.4%) living in rural areas were found T. canis positive, compared to about one-quarter of the dogs (26.2%) from urban areas. Analysis by provenance and role revealed the highest infection rate in rural hunting dogs (64.7%) and the lowest in urban companion dogs (22.1%). According to questionnaire data, the peridomestic environment, i.e. gardens and dog pens, is the most important defecation site in both rural and urban areas. Since over 40% of the dogs who defecate in dog pens are infected and 24% of urban and 47% of rural dogs who leave their droppings in the house surroundings harbour the parasite, it is clear that these environments may constitute sites of zoonotic risk. Our analysis of soil samples from 60 farms confirmed the high contamination level, revealing positive soil samples in more than half of the farms. Substantial egg contamination was also found in urban areas, as 3/6 parks examined were Toxocara spp. positive. Finally, our serological findings indicate that human infection actually occurs in the area: 7 out of 428 adults examined (1.6%) had very high levels of antibodies to T. canis antigen, suggesting a previous contact with the Larva migrans of the nematode.     

Anthelmintic effect of levamisole hydrochloride or ivermectin on tissue toxocariasis of mice

Paranatal transmission of Toxocara canis infection could be prevented in pups if an effective drug were administered to pregnant bitches. This drug also could eliminate the larvae in dogs that have been experimentally infected repeatedly to produce protective immunity. For these reasons, we assayed the effect of 2 doses of levamisole hydrochloride or ivermectin on T canis larvae. Mice (5 groups) were infected with 1,000 infective T canis larvae and then treated with 2 different dosages of levamisole hydrochloride (6 mg/kg or 12 mg/kg, given subcutaneously), 2 different dosages of ivermectin (0.2 mg/kg or 0.4 mg/kg, given IM) or 0.15M NaCl (given subcutaneously) once a day from days 15 to 28 of infection. On day 33 of infection, the parasites in liver, lungs, brain, and carcass were obtained and compared between groups. The smaller dosage of levamisole hydrochloride (6 mg/kg) significantly decreased only carcass parasitism to 17% of that in the controls, but did not affect significantly the total parasite load. The larger dosage of levamisole hydrochloride (12 mg/kg) decreased the infection in all organs, but particularly in carcass and brain; total parasitism was only 36% of that in the controls. The smaller dosage of ivermectin (0.2 mg/kg) significantly increased the number of larvae in the lungs to 550% of that in the controls, but it did not significantly affect the total parasite load. The larger dosage of ivermectin (0.4 mg/kg) significantly decreased only brain parasitism, but liver and total parasitism were decreased to 40% and 57%, respectively, compared with that in the controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevalence of dog intestinal parasites and risk perception of zoonotic infection by dog owners in São Paulo State, Brazil

Coprological examination was used to estimate the prevalence of gastrointestinal parasites in stray and domiciled dogs from Botucatu, S?o Paulo State, Brazil. Risk factors for dog infection were assessed in relation to demographic, husbandry and management data. The dog owners completed a questionnaire survey on some aspects of dog parasitism such as parasite species, mechanisms of infection, awareness of zoonotic diseases and history of anthelmintic usage. Parasites were found in the faeces of 138 dogs, with an overall prevalence of 54.3%. Dogs harbouring one parasite were more common (31.4%) than those harbouring two (18.5%), three (3.2%) or four (1.2%). The following parasites and their respective frequencies were detected: Ancylostoma (37.8%), Giardia (16.9%), Toxocara canis (8.7%), Trichuris vulpis (7.1%), Dipylidium caninum (2.4%), Isospora (3.5%), Cryptosporidium (3.1%) and Sarcocystis (2.7%). Stray dogs were found more likely to be poliparasitized (P<0.01) and presented higher prevalence of Ancylostoma, T. canis and Giardia (P<0.01) than domiciled ones. Toxocara canis was detected more frequently in dogs with <6 months of age (P<0.05) and no effect of sex or breed could be observed (P>0.05). Except for Ancylostoma, that showed a significantly higher prevalence in dogs living in a multi-dog household (P<0.01), parasite prevalences were similar in single- and multi-dog household. The answers of dog owners to the questionnaire showed that the majority does not know the species of dog intestinal parasites, the mechanisms of transmission, the risk factors for zoonotic infections, and specific prophylactic measures. The predominance of zoonotic species in dogs in the studied region, associated with the elevated degree of misinformation of the owners, indicates that the risk of zoonotic infection by canine intestinal parasite may be high, even in one of the most developed regions of Brazil.     

Activity of ivermectin against canine intestinal helminths

The anthelmintic activity of ivermectin was tested in 98 dogs against adult ascarids (Toxocara canis, Toxascaris leonina), hookworms (Ancylostoma caninum, A braziliense), and whipworms (Trichuris vulpis), and against experimentally induced infections (4th-stage larvae) of T canis and A caninum. Dosage levels tested were single subcutaneous injections of 50, 100, 200, or 400 micrograms/kg of body weight with appropriate vehicle-treated controls. A minimum of 4 (usually 5) dogs were tested with each parasite and dosage level. The lowest dosage level, 50 micrograms/kg, and all higher dosage levels expelled greater than 99% of the adult forms of both species of hookworms and intestinal larval forms of A caninum, as determined by worm counts at necropsy. A dosage level of 100 micrograms/kg was required to expel greater than 99% of whipworms and 200 micrograms/kg was necessary to expel adult (91%) and larval (97%) stages of T canis. Ivermectin was only marginally effective (34.2%, 46.2%, 69.2%, and 53.8%) against Toxascaris leonina at 50, 100, 200, and 400 micrograms/kg, respectively, and had no effect against occasional infections with the tapeworms, Dipylidium caninum (14 dogs) and Taenia spp (3 dogs).     

Ascarid infections of cats and dogs

The ascarids Toxocara canis, Toxocara cati, and Toxascaris leonina are probably the most common gastrointestinal helminths encountered in small animal practice. Both T. canis and T. cati can cause serious disease in kittens and puppies; T. leonina is generally less pathogenic. Prenatal transmission assures that virtually all puppies are born infected with T. canis. Transmammary transmission is probably the major route of infection for kittens with T. cati. In addition, all three species of worm produce resistant eggs and use paratenic hosts to facilitate transmission. Much is now known about the complex biology and life history of T. canis. However, many questions, such as those concerning the mechanisms of larval survival within host tissues and of larval reactivation and migration during pregnancy, await further study. The mechanism of resistance to ascarid infections in cats and dogs has not been clearly defined. Ascariasis is traditionally thought to be a disease of young animals, with older animals being considered immune. However, at least in the case of T. canis, adult dogs can be repeatedly infected. A wide range of anthelmintics is available with extremely high efficacy against patent ascarid infections. The problem of prenatal infection with T. canis may be overcome by strategic use of the newer benzimidazole-carbamates, and the production of ascarid-free puppies now seems possible. However, complete larvicidal activity against somatic stages has not been convincingly demonstrated. Visceral larva migrans-like syndromes are now being recognized in dogs and cats. In addition, visceral larva migrans in children due to T. canis continues to be a significant zoonotic disease in North America and underscores the need for the veterinary profession to control ascarid infections in cats and dogs at every opportunity.     

477例门诊犬寄生虫种类和感染情况的调查

对2012年-2015年西北农林科技大学西安动物医院门诊确诊的477例犬寄生虫感染资料进行分类统计和分析,以期了解西安地区犬寄生虫的种类和感染情况,对犬寄生虫的防控提供依据。结果显示,从感染犬中共检出14种寄生虫,每种寄生虫的阳性率依次为:吉氏巴贝斯虫51.79%(247/477),等孢球虫16.15%(77/477),贾第鞭毛虫11.74%(56/477),犬弓首蛔虫6.71%(32/477),疥螨4.41%(21/477),蠕形螨4.41%(21/477),犬复孔绦虫3.78%(18/477),犬钩口线虫2.31%(11/477),犬耳痒螨1.89%(9/477),吸吮线虫0.63%(3/477),华支睾吸虫0.42%(2/477),弓形虫0.42%(2/477),犬尾旋线虫0.21%(1/477),犬恶丝虫0.21%(1/477)。混合感染两种及以上寄生虫的犬占5.45%(26/477)。肠道寄生虫中的等孢球虫、贾地鞭毛虫、犬弓首蛔虫和犬钩口线虫等容易发生混合感染。寄生虫和病毒合并感染犬占8.39%(40/477),犬细小病毒(CPV)、犬瘟热病毒(CDV)和犬冠状病毒(CCV)常与犬肠道寄生虫合并感染。许多寄生虫感染与犬的年龄有密切关系,季节对寄生虫感染也有影响。原虫感染特别是吉氏巴贝斯虫感染应当引起重视。控制犬与寄生虫传播媒介的接触、改善犬的饲养管理条件对寄生虫感染的预防十分重要。     

Investigations into the prevention of prenatal and lactogenic Toxocara canis infections in puppies by application of moxidectin to the pregnant dog

Aim of the investigation was to examine whether two administrations of moxidectin to pregnant dogs could prevent pre-natal and lactogenic infections of puppies with reactivated Toxocara canis larvae. Four pregnant beagles, infected experimentally with 20 000 embryonated eggs of T. canis, were treated subcutaneously with 1 mg moxidectin per kg body weight on days 40 and 55 of pregnancy (5-13 days before parturition). One further dam and its puppies served as untreated control. Two applications of moxidectin completely prevented pre-natal and lactogenic infections in the puppies. Neither intestinal stages nor somatic larvae were found in the dams or their corresponding puppies. All puppies and dams of the treatment group remained coproscopically negative until 42 days after parturition. The administration of moxidectin did not show any side effects in the dams. None of the puppies of the treated dams showed any pathological abnormalities. In the untreated dam one adult and 26 somatic larvae of T. canis were detected at necropsy. All puppies of the untreated dam showed a patent T. canis infection from day 28 post-natum (p.n.); 296 pre-adult and adult stages of T. canis were spontaneously eliminated and 51 intestinal stages and five somatic larvae of T. canis were recovered at necropsy. In contrast to the puppies of the treated dams all negative control puppies showed blood eosinophilia after parturition and elevated liver enzyme levels.     

DISTRIBUTION AND DIAGNOSIS OF DIROFILARIASIS AND TOXOCARIASIS IN AUSTRALIA

SUMMARY: The prevalence of Dirofilaria immitis infection in dogs continues to increase in the temperate east coast zone of Australia (and is extending further south into New South Wales and Victoria). However, the infection rate has not changed in the tropics over the past 10 years where it would appear that a maximum infection rate of 90% occurs in a given Australian dog population. Twelve percent of Brisbane dogs had occult dirofilariasis and it is suggested that the proportion of occult infections was probably higher in the tropics. Dogs of all breeds appear equally susceptible to D. immitis with infection being more common in older male dogs. The level of microfilaraemia was, occasionally, proportional to the number of heartwprms per dog. Toxocara canis was present in about 75% of dogs from all areas studied except in Central Australia where the level of infection was much lower.
Immunodiagnosis of D. immitis and T. canis with high specificity and sensitivity was achieved by cyanogen bromide indirect fluorescent antibody and cell-mediated immunity tests using parasite antigens purified by affinity chromatography. These tests enabled occult dirofilariasis to be differentiated from unrelated canine cardiac and pulmonary failure. Such immunodiagnosis can aid in the early diagnosis of dirofilariasis particularly in situations where no circulating microfilariae can be detected.
The prevalence of serum antibody in man to purified Dirofilaria and Toxocara antigens was proportional to the incidence of respective canine infections at each location.     

Larval development of Toxocara canis in dogs

The parasitic roundworm Toxocara canis is present in dog populations all over the world. Due to its zoonotic potential, this roundworm is of special interest not only for veterinarians, but also for medical practitioners. In the present review, current knowledge of infection routes and the subsequent development of larvae within the canine host is summarised. Furthermore, information about the clinical, pathological, enzymatic, haematological and histopathological changes was collected, giving a broad overview of current knowledge of the infection. Although the data collected over the years give an idea of what happens during the larval development of T. canis, many questions remain open. Nevertheless, it is important that we continue our efforts to further understand the biology of this versatile and compelling parasite and try to improve and optimise strategies to prevent the infection in dogs and thereby to protect humans from this infection.     

Risk of Toxocara canis eggs in stray and domestic dog hair in Egypt

The aim of the study was to assess whether the hair of stray and domestic dogs in Egypt was contaminated with the eggs of the zoonotic parasite Toxocara canis, and also to identify risk factors for T. canis for contamination. Paired samples of hair and feces were collected from 53 stray and 47 domestic dogs, and hair samples were obtained from a further 11 stray and 9 domestic dogs. All samples were examined to identify T. canis eggs and, if eggs were found, their maturation stage. Eggs were identified in 26.6% of stray and 10.7% of domestic dog's hair samples. A significantly increased risk of embryonated T. canis eggs in hair samples was found in stray dogs (p=0.04), stray dogs had 3.18 (95% CI: 1.04-9.74) times the odds of having T. canis eggs present compared with domestic dogs. There was also a significant difference (p=0.02) between the mean quantity of eggs per gram in stray (77.6±6.54) and domestic (48.7±6.65) dog's hair. Fecal examination found a T. canis egg prevalence of 35.8% and 21.3% in stray and domestic dogs, respectively. As no domestic dogs which were positive from hair samples had negative fecal samples, this indicates that the presence of T. canis eggs in hair is probably due to self contamination. Two stray dogs had positive hair samples but negative fecal samples indicating that contamination may also be environmental. As both non-embryonated and embryonated T. canis eggs were found in the hair of domestic dogs, direct contact with dogs may be a potential risk factor for transmission of T. canis eggs to humans.     

Efficacy of moxidectin 6-month injectable and milbemycin oxime/lufenuron tablets against naturally acquired toxocara canis infections in dogs

The efficacy of moxidectin injection (ProHeart 6 Sustained Release Injectable for Dogs, Fort Dodge Animal Health) against naturally acquired infections of Toxocara canis was compared with that of milbemycin oxime/lufenuron tablets (Sentinel Flavor Tabs, Novartis Animal Health). Eighteen dogs with naturally acquired infections of T. canis were ranked by egg counts and randomly assigned to treatment with moxidectin (170 micro g/kg), milbemycin (500 micro g/kg)/lufenuron (10 mg/kg), or to an untreated control group (six dogs per treatment). Dogs were euthanized 7 days after treatment for recovery, identification, and enumeration of parasites by species. There was no apparent efficacy for moxidectin against T. canis. Conversely, milbemycin oxime/lufenuron was 91.5 % effective against naturally occurring infections of this canine parasite.     

Effect of fenbendazole on Toxocara canis larvae in tissues of infected dogs.

The effect of fenbendazole therapy was studied in six dogs fed 10,000 embryonated Toxocara canis eggs. At 47 days after they were fed T canis, four dogs were given fenbendazole in two divided doses totaling 50 mg/kg of body weight each day for 14 days. Two infected dogs were not given fenbendazole. All dogs were necropsied at the end of treatment and the foci were counted in the lungs; their skeletal muscles were digested in 1% trypsin for the recovery of larvae. The T canis larvae were not recovered from the skeletal muscle of the four infected dogs treated with fenbendazole; 15 and 42 larvae/100 g of skeletal muscle were recovered from the two nonmedicated infeected dogs. The number of grossly visible foci on surfaces of lungs in treated dogs was markedly less than in the nonmedicated infected dogs. The results indicate that fenbendazole might be effective in preventing prenatal infection in dogs.     

Contamination of dog hair with eggs of Toxocara canis

Toxocara canis, the common intestinal nematode of dogs and foxes, is the parasite responsible for human toxocarosis. It has recently been shown that dogs may harbour eggs of the parasite in their fur. To further investigate this claim a population of 100 stray dogs was examined to establish the prevalence and intensity of adult toxocaral worm infection in the intestines and eggs harboured in the hair. A novel method of washing the eggs from the hair was used. Sixty-seven percent of dogs were found to have T. canis eggs on their hair with a mean egg retrieval of nearly 584 eggs per gram from positive dogs. The age of the dog was found to be the only significant factor to influence the prevalence and intensity of eggs, with 95% of all the eggs recovered found on puppies. Thirty-nine percent of dogs were found to have adult T. canis worms in their intestine, although a significantly higher percentage of puppies (80%) were infected with worms than adults (22.5%). Puppies also had more worms per infection than adults and have a strong positive correlation between egg and worms numbers whereas adults did not. These studies show that stray dogs, particularly puppies, potentially harbour considerable numbers of eggs on their hair, at densities far higher than those reported in the soil or the general environment.     

Prenatal and transmammary infections of Toxocara canis in dogs: effect of benzimidazole-carbamate anthelmintics on various developmental stages of the parasite

Fenbendazole and albendazole, given at a dose rate of 150 mg/kg for 3 days, produced a 90 per cent reduction in the numbers of second stage larvae of Toxocara canis present in the tissues of dogs although no reduction in the number of larvae found in the brains of infected dogs occurred with this treatment. The results suggest that a course of 3 day therapy with these anthelmintics should prevent prenatal infections in puppies. However, if infection is acquired by bitches during late pregnancy or early lactation, the transmammary route of infection becomes important. Therefore, anthelmintic treatment of the bitch prior to pregnancy will not prevent transmission of infection to her puppies should the bitch acquire a new infection of T. canis during pregnancy or early lactation. Alternatively, infection with T. canis can be controlled through the treatment of neonatal puppies for migrating larvae of T. canis. Treatment of newborn puppies with fenbendazole, albendazole or oxfendazole at a dose of 100 mg/kg for 2–3 days produced a 91–99 per cent reduction in the number of adult parasites found. In addition, a single dose of fenbendazole, given at a dose rate of 40 mg/kg, eliminated 93–96 per cent of adult T. canis from the intestines of 4–5-week-old puppies. These latter treatments would need to be repeated to eliminate completely the infection from puppies.     

Epidemiological study of non-systemic parasitism in dogs in southeast Mediterranean Spain assessed by coprological and post-mortem examination

The prevalence and risk factors of non-systemic canine ecto- and endoparasitism and anthelminthic use in Murcia located at the centre of the Spanish Mediterranean coastal arch, was investigated by coprology and necropsy in up to 275 pet, city shelter and stray dogs in 2001-2004. Faecal parasite stages were detected in 25% of dogs. Species frequency was 6-10% for Toxocara canis, Ancylostomatidae spp., Toxascaris leonina and Isospora canis, and 0.4-1% for Trichuris vulpis, Giardia lamblia, and Dipylidium caninum. Logistic regression indicated that the risk of intestinal parasitism was highest for dogs 相似文献   

Toxocara canis infection induces antigen-specific IL-10 and IFNgamma production in pregnant dogs and their puppies

Toxocara canis (T. canis) is originally a parasite of canine bitches and their pups. The pathogenicity of T. canis infection is enhanced during pregnancy and puppyhood. The aim of this study was to investigate if modification of IFNgamma and IL-10 secretion occurs during infection in pregnant dogs and puppies. Analysis of cytokines secreted could let us hypothesize a role for IL-10 and/or IFNgamma in T. canis infection. We tested T. canis-specific production of IFNgamma and IL-10 by lymphocytes of pregnant dogs and their puppies after in vitro re-exposure to purified excretory/secretory antigen (ESAg) from T. canis. Blood mononuclear cells (BMC) isolated from pregnant dogs and their puppies were cultured in the presence of ESAg. Cultures' supernatants were tested for cytokine levels by ELISA. Results obtained showed that IL-10 concentrations increased during pregnancy in infected animals and in the meantime IFNgamma production decreased. In puppyhood, we observed that, IL-10 concentration decreased with the age of puppies mainly in infected animals while IFNgamma increased. In conclusion, our data suggests that BMC of infected dogs have a particular modification of IL-10 and IFNgamma synthesis. These data could be the basis to design immunotherapeutic approaches.     

Toxocara eggs shed by dogs and cats and their molecular and morphometric species-specific identification: is the finding of T. cati eggs shed by dogs of epidemiological relevance?

Intestinal infections with Toxocara cati and Toxocara canis in their definitive host (felids and canids, respectively) are diagnosed by egg identification in faeces using coproscopical techniques. The Toxocara species is assumed to comply with the species from which the examined faeces were obtained, i.e. T. cati in cats and T. canis in dogs. We isolated and measured Toxocara eggs from faecal samples of 36 cats and 35 dogs from Switzerland and identified the Toxocara species by PCR. Amongst the isolates originating from dogs, 24 (68.5%) were determined as T. canis and 11 (31.5%) as T. cati. In all samples originating from cats, only T. cati was identified. Based on PCR identification, eggs of T. canis (n=241) and T. cati (n=442) were measured, revealing statistically significant different (p<0.001) mean sizes of 62.3 by 72.7 μm for T. cati and 74.8 by 86.0 μm for T. canis eggs. Considering that coprophagy is not unusual for dogs, a considerable percentage of Toxocara infections coproscopically diagnosed in dogs, as well as assumptions on anthelminthic resistance in regularly treated dogs, might in fact relate to intestinal passages of eggs following the uptake of other animals' faeces.     

Efficacy of selamectin against experimentally induced and naturally acquired ascarid (Toxocara canis and Toxascaris leonina) infections in dogs

The efficacy of selamectin against adult ascarids was evaluated in eight controlled and masked studies in dogs. Three laboratory studies evaluated selamectin against experimentally induced infections of Toxocara canis; three laboratory studies evaluated selamectin against naturally acquired infections of T. canis; one laboratory study evaluated selamectin against naturally acquired infections of both T. canis and Toxascaris leonina; one field study evaluated selamectin against naturally acquired infections of ascarids (T. canis and/or T. leonina) in dogs presented as veterinary patients. Selamectin was administered topically to the skin of dogs in unit doses designed to deliver a minimum of 6mgkg(-1) (range, 6-12mgkg(-1)). In all studies, dogs were allocated randomly to treatment assignments (selamectin or vehicle control in laboratory studies: selamectin or reference product in the field study) on the basis of pretreatment fecal egg counts. For induced infections, there were significant reductions in geometric mean numbers of adult T. canis after a single application of selamectin (93.9-98.1%, P=0.0001), after two monthly applications (> or =88.3%, P< or =0.0001), and after three monthly applications (100%, P< or =0.0002). In the natural infection laboratory studies, when selamectin was administered twice at an interval of 30 days, the percentage reductions in geometric mean numbers of adult T. canis at necropsy were 84.6, 91.3, and 97.9%, and when selamectin was administered on days 0, 14, and 30, the percentage reductions were 91.1 and 97.6%. Geometric mean fecal T. canis egg counts were reduced by > or =92.9% (P< or =0.0067) at the end of the studies. In the field study, geometric mean fecal ascarid egg counts were reduced by 89.5 and 95. 5% (P=0.0001) for 14 and 30 days, respectively, after a single treatment with selamectin, and by 94.0% (P=0.0001) 30 days after the second treatment with selamectin. These reductions compared favorably with the egg count reductions from dogs treated with a reference product containing praziquantel, pyrantel embonate, and febantel. There were no adverse drug experiences or treatment-related mortalities during any of the studies. Selamectin, when administered topically in a unit dose providing a minimum dosage of 6mgkg(-1), was safe and effective against adult T. canis and T. leonina and in reducing the fecal excretion of T. canis eggs in dogs.     

Immunity against Babesia rossi infection in dogs vaccinated with antigens from culture supernatants

Soluble parasite antigens (SPA) from different Babesia species have been shown earlier to induce protective immunity when used as vaccine. However, initial attempts to produce such vaccine against Babesia rossi infection using SPA from B. rossi culture supernatants were not or only partially successful. Here we show that when dogs were vaccinated with a vaccine comprising SPA from B. rossi combined with SPA from Babesia canis protective immunity against experimental challenge infection was induced. Immunity was reflected in reduced clinical signs that resolved spontaneously, and reduction of parasitaemia and SPA in the blood. Not a single infected erythrocyte could be found in blood smears of dogs that had been repeatedly boosted (three vaccinations in total). In contrast, three out of four control dogs required chemotherapeutic treatment to prevent death. The fourth control dog showed a transient parasitaemia that resolved spontaneously. Vaccination did not prevent the development of a transient anaemia. It is concluded that a vaccine containing a mixture of SPA obtained from in vitro culture supernatants of B. rossi and B. canis induces protection in dogs against heterologous challenge infection with B. canis (as shown before) or B. rossi.