Parasitol Res (2009) 105:S75–S81
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DOI 10.1007/s00436-009-1498-6
Treatment and Prevention of Vertical Transmission of Toxocara cati in Cats with an Emodepside/Praziquantel Spot-on Formulation
Sonja Wolken1 ( ), Roland Schaper2, Norbert Mencke2, Friederike Kraemer1, Thomas Schnieder1 1 2
Institute for Parasitology, University of Veterinary Medicine Hannover, Germany Bayer Animal Health GmbH, Leverkusen, Germany
E-mail:
[email protected]
Abstract This study aimed to determine the efficacy of emodepside 2.14 %/praziquantel 8.58 % topical solution (Profender®, Bayer) in the prevention and treatment of lactogenic Toxocara cati infections. Eight pregnant cats were orally infected with T. cati eggs during late pregnancy. Four queens were treated on day 60 post conception and four queens were left untreated. The kittens of two untreated queens were treated 28 days after birth. The two other negative control litters were left untreated. The efficacy of emodepside was determined by faecal egg counts. While faecal samples of queens and litters in the control group became positive for T. cati, egg shedding was completely prevented in all four treated queens, in their litters and in the kittens from the two litters which were treated four weeks after birth. The untreated mothers of the latter stayed also coproscopically negative, which might
be explained by an oral uptake of emodepside through grooming. The treatment was well tolerated by pregnant queens as well as by four-weeks-old kittens. To our knowledge, this is the first publication that focuses on the prevention of lactogenic transmission of T. cati.
Introduction Toxocara cati (Nematoda: Ascaridoidea) is the most common gastrointestinal helminth of cats worldwide (Fig. 1). Cats can become infected with T. cati either by ingestion of larvated eggs, ingestion of paratenic hosts that harbour T. cati larvae or by lactogenic transmission in which larvae are passed via milk from a queen to her suckling kittens (Fig. 2). Prenatal infections are not observed (Coati et al. 2004; Swerczek et al. 1971).
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Fig. 1 Adults of Toxocara cati in the small intestine of a cat
Although less frequently diagnosed, T. cati can cause human toxocarosis like Toxocara canis. After the ingestion of larvated T. cati eggs, humans may develop visceral or occular larva migrans (Overgaauw 1997). Recent investigations demonstrated high prevalences of T. cati, not only in stray cats, but also in pet animals (see Table 1). Besides hygiene measures, frequent anthelminthic treatments are the main strategy to face the risk of zoonotic transmission. Numerous substances including moxidectin, selamectin, fenbendazole, flubendazole, piperazine, milbemycin and pyrantel have shown their safety and efficacy in removing ascarid infections. In contrast to dogs where diverse studies have focused on the prevention of neonatal infections by T. canis (Kraemer et al. 2006), no data are available concerning the treatment of pregnant queens in order to prevent lactogenic transmission of T. cati. The aim of this study was to evaluate the efficacy of emodepside, a novel anthelmintic of the cyclooctadepsipeptide class, in the prevention of lactogenic infections with T. cati and to evaluate its tolerability and efficacy in young kittens infected with T. cati via their mother. The formulation investigated in this study is a spoton combination of emodepside and praziquantel (Profender® spot-on).
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Fig. 2 Life cycle of Toxocara cati
Materials and methods Experimental animals Eight female cats (domestic short hair) aged between 3 and 9 years and originating from the cat colony of the Institute for Parasitology, University of Veterinary Medicine Hannover, were included in the study. Queens and their litters were individually housed in tiled indoor kennels with a floor space of at least 3.5 m2. The kennels were cleaned with 60–80 °C hot water and disinfected with cresole (Neopredisan®, Menno Chemie) on a regular basis. The cats were fed standard diets (Mature S/O®, Royal Canin), had access to water ad libitum and received amusement toys for environmental enrichment as well as daily grooming time with the animal attendants. Mating, parturition and rearing proceeded under natural conditions. The study was conducted during several breeding seasons. Whenever a cat of the colony showed signs of oestrus, it was brought together with the tomcat. The day after mating had been observed was defined as the day of presumed conception (study day –60). Conception was confirmed by measuring the serum progesterone level shortly after mating, and the number and viability of the foetuses was determined in ultrasound examinations approxi-
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mately four weeks after mating. The kittens stayed together with their mothers for eight weeks after birth. Health observations General health observations were conducted daily by the animal attendants. Physical examinations of the queens were performed by a veterinarian before mating and on the day before treatment. The
kittens were physically examined one to two days post partum and the day before treatment. Clinical assessments (systemic and at the site of spot-on application) were performed on the treated cats pre treatment, 3 and 24 hours post treatment and thereafter on a weekly basis for four weeks after treatment to detect any adverse events. Cats were weighed before treatment.
Table 1 Toxocara cati prevalence found in various surveys Date of survey or year of publication (a)
Country
Sample population (n)
Prevalence
Reference
2005–2006
Iran
Stray cats post mortem (114)
42.6 %
Mohammad et al. 2007
2006
Qatar
Stray cats post mortem (488)
0.8 %
Abu-Madi et al. 2008
Shelter cats, faecal sampling (491)
4.9 %
Cats visiting vet clinic, faecal sampling (572)
1.7 %
2004–2005
Australia
Palmer et al. 2008
2004
Iran
Stray cats post mortem (100)
44 %
Sharif et al. 2007
1996–2003
Chile
Cats visiting vet practice, faecal sampling (230)
10 %
Lopez et al. 2006
2004a
Spain
Stray cats, faecal sampling (231)
20.3 %
Farm cats, faecal sampling (48)
25 %
Household cats, faecal sampling (103)
2004a
Miro et al. 2004
10.7 %
Feral cats, faecal sampling (100)
21 %
Household cats, faecal sampling (76)
18 %
USA
Nutter et al. 2004
1998–2002
Germany
Samples at diagnostic lab (441)
3.9 %
Epe et al. 2004
1999–2002
Germany
Samples at diagnostic lab (3167)
6.4 %
Barutzki and Schaper 2003
2006–2007
Germany
Cats at arrival at shelter, faecal sampling (837)
27.7 %
Rohen 2009
2004a
Brazil
Stray and shelter cats, faecal sampling (135)
25.2 %
Labarthe et al. 2004
2004a
The Netherlands
Shelter cats, faecal sampling (305)
28.2 %
Robben et al. 2004
2003a
Mexico
Household cats in Mexico city, faecal sampling (520)
42.5 %
Martinez-Barbabosa et al. 2003
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Experimental infections Toxocara cati eggs were recovered from the faeces of an experimentally infected cat. The strain originated from a field isolate identified in northern Germany in 1995. The eggs were incubated at 25 °C for six weeks and stored in petri dishes in tap water thereafter at 4 °C until application. Before infection, the viability of the larvae was microscopically checked. Starting 50 days after the presumed conception, each pregnant cat was infected daily with approximately 2,000 infective T. cati eggs for 11 consecutive days (study day –10 to 0). The eggs were suspended in tap water and applied orally with a syringe.
Where possible, queens with higher expected litter size per ultrasound diagnosis (n > 3) were allocated to group B. Queens of group A were treated with Profender® spot-on at a minimum dosage of 3 mg emodepside/kg body weight and 12 mg praziquantel/kg body weight according to label instructions of the manufacturer. Kittens of group B1 were treated with the smallest available pipette (weight range 0.5 to 2.5 kg body weight), although with the exception of one kitten they did not possess the minimum bodyweight of 0.5 kg at the time of treatment. The kittens were separated from each other and from the mother for four hours after treatment.
Allocation and treatment Group allocation and treatments are summarised in Table 2. Eight cats were assigned to group A and B with four cats each. Animals of group A were treated 60 days after presumed conception (study day 0, 5 days before expected parturition). Cats of group B served as untreated control. After birth, queens and litters of group B were further split in group B1 and B2 with two queens and her kittens in each group. Kittens of group B1 were treated 28 days after birth, while kittens of group B2 were further left untreated. In order to have a reasonable number of kittens in study group B1 and B2, the assignment of queens to group A and B was not based on random draw.
Parasitological examinations Faecal samples from queens and kittens were examined using a quantitative method (Wetzel 1951) that provided a measure of the parasite egg count per gramme faeces (EPG). Before infection, three samples were taken from the queens to demonstrate the absence of patent T. cati infections. Sampling of queens was started at the latest from 30 days after birth. Sampling of kittens was started as soon as the mother stopped the removal of faeces during grooming. This was possible 35 days after birth at the latest. Sampling was performed seven days per week until 56 days after birth. Faeces of kittens were pooled by litter.
Table 2 Group allocation and results of faecal egg counts Study group
Queen
No. of kittens
1
2
2
2
A 3
2
4
4
5
4
B1 6
2
7
3
B2 8
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5
Treated stage
EPG
queen
Negative in queens and kittens
kittens
Negative in queens and kittens
none
Positive in queens and kittens
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Results Establishment of patent T. cati infections in the control animals The acute infection during late pregnancy produced patent infections in both queens of study group B2 and in their eight kittens. One queen became coproscopically positive for T. cati 50 days after the first inoculation. The corresponding litter became positive 36 days after birth. Egg shedding in the other queen started 59 days after the first inoculation with T. cati. The kittens of the second queen became coproscopically positive 50 days after birth. EPG counts reached a maximum of 22,233. All cats of the control group stayed clinically healthy during the course of the study. Prevention of lactogenic transmission of T. cati by Profender® spot-on Four queens of study group A were treated with Profender® spot-on topical solution five days before expected parturition. In retrospect, two queens were treated five days and two queens were treated six days before parturition. The treatment was well tolerated by the pregnant queens. No systemic or local side effects could be detected. The gestation time was within physiological ranges and there was no indication of a negative influence of the treatment on the unborn kittens. Beside one kitten suffering from a humerus fracture due to an accident, no abnormal findings were detected in the kittens. None of the queens developed a patent T. cati infection until the end of the study (56 days after parturition). The queens in group A gave birth to a total of ten kittens. All litters stayed coproscopically negative throughout the study. Tolerance and efficacy of Profender® spot-on in four-weeks-old kittens In study group B1, a total of six kittens was treated with Profender® spot-on 28 days after birth. None of these kittens developed a patent T. cati infection until study end (day 56 after birth). The kittens were treated at a body weight of 0.51 kg,
0.47 kg, 0.39 kg, 0.44 kg, 0.42 kg and 0.39 kg. The treatment was well tolerated by all six kittens. No local or systemic side effects were seen. The kittens developed normally without any evidence for a delayed or disturbed growth. Beside one queen of the negative control group giving birth to two dead kittens, no abnormal findings were present in study group B1. The two mothers of the treated kittens stayed coproscopically negative throughout the study period.
Discussion First objective of this study was to determine the efficacy of emodepside in the prevention of lactogenic T. cati transmission when administered in a spot-on combination of emodepside/praziquantel (Profender® spot-on) to queens with an acute T. cati infection. The method of infection performed in this study was previously shown to be effective in producing an acute T. cati infection in queens and vertically infected kittens (Coati et al. 2004). In this study, two queens and their corresponding litters served as untreated control group. Both cats and their offspring developed patent T. cati infections, demonstrating the functionality of the method of infection. In study group A, it could be demonstrated that one topical treatment with Profender® spot-on during late pregnancy (5 to 6 days before birth) completely prevented egg shedding in four queens and their ten kittens. For animal welfare reasons, the efficacy was based on faecal egg counts. No necropsies on kittens or removal and examination of the mammary glands of the queens as well as no examinations on milk samples were performed. Furthermore, parturition and rearing was performed under natural conditions. Except for the treated kittens that were separated from the mother for four hours after treatment, no separation between queens and kittens was performed. Therefore the study design does not allow to draw the conclusion that the absence of patent T. cati infections in the kittens of
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treated mothers is exclusively based on elimination of infective larvae from the queen. Beside the possibility of an oral uptake of active ingredient via milk, the mode of treatment (spot-on) leaves also the chance of substance transmission from the mother to the kittens during grooming. Although the parasitologic technique used in this study cannot prove that vertical transmission did not occur, it seems unlikely that the prevention of egg shedding in the kittens was a result of emodepside activity in the kittens after a vertical transmission of larvae. It is known that larvae are already transmitted during the first five days of nursing (Swerczek et al. 1971). Therefore it seems unrealistic that active ingredient in concentrations high enough to kill the larvae in the kittens was delivered via milk before a killing of T. cati larvae directly within the mammary glands occurred. Concerning the substance transfer via contact, it seems conceivable that licking the fur of a treated animal may result in an uptake of emodepside in concentrations high enough to eliminate an existing infection (see below). Nevertheless it appears unlikely that this was the mode of action in study group A, as grooming behaviour occurs mainly in the direction of the kittens. Taken together with the fact that approval studies for Profender® spot-on demonstrated a high efficacy of emodepside on T. cati larvae (Reinemeyer et al. 2005) and accordingly the formulation has a claim not only for adult stages of T. cati, but also for third- and fourth-stage larvae and immature adults, it seems likely that a vertical transmission of T. cati was prevented. Second objective of this study was to obtain data on the efficacy and tolerance of an emodepside/praziquantel treatment in four-weeks-old kittens. Six kittens in study group B1 were treated 28 days after birth with the smallest Profender® spot-on pipette (weight range 0.5–2.5 kg). The treatment was well tolerated by all kittens. All EPG counts were zero until study end (day 56 after birth). The mothers of these kittens stayed coproscopically negative as well, which could be explained by an oral uptake of emodepside through grooming. Although
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the kittens were separated from the queens for four hours after treatment, this might not have been long enough for a complete resorption of active ingredient and later prevention of a transfer to the queens. To our knowledge this is the first publication that focuses on the prevention of lactogenic transmission of T. cati. To date, none of the anthelmintics registered for cats has a claim on the prevention of vertical transmission. Keeping in mind that this study was conducted under laboratory conditions and that high doses were chosen for infection of the queens, our results concerning the high egg output in the control animals and larvae recovery rates from vertically infected kittens found in other surveys (Coati et al. 2004; Swerczek et al. 1971) lead to the assumption, that lactogenic transmission is an effective survival strategy of the parasite. Although animal numbers were low in the study presented here, there is strong evidence that a single treatment of the queen with Profender® spot-on during late pregnancy can prevent the lactogenic transmission of T. cati to kittens and could therefore be taken as a useful tool in the strategic control of the parasite.
Acknowledgements All animal experiments complied with the German National Code for Animal Protection (Tierschutzgesetz), issued May 2006 (Version of December 2007). This study was funded by Bayer Animal Health GmbH.
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