TABLE 1 The survival rate for poisoned dogs and cats
SHORT CONTRIBUTIONS
A retrospective study of poisoning cases in dogs and cats: comparisons between a rural and an urban practice School of Veterinary Studies, Murdoch University, Murdoch, Western Australia 6150
ID ROBERTSON
Brookton Veterinary Hospital. Box 84, Brookton, Western Australia 6306
M LEGGOE
School of Veterinary Studies, Murdoch University, Murdoch, Western Australia 6150
PR DORLING SE SHAW WT CLARK
Poisoned dogs and cats often require emergency treatment by aveterinary practitioner. Ifpractitioners areawareofthoseagents commonly associated with poisonings in their locality, diagnosis may be achieved more rapidly enabling prompt treatment to be instigated to improve the animal’s chance of survival and reduce the anguish of the owner. The relative importance of specific poisons may vary in different geographic regions, depending on such factors as the type of pesticides commonly used, the flora and fauna present in the regions, the different practices in handling and housing domestic pets, and the population density of the exposed species (Studdert 1 9 8 5 Osweiler ~ 1983). There is little information available on the prevalence of specific poisonings in dogs and cats in Western Australia. A retrospective study was undertaken using computerised records from 2 sources, namely, the Murdoch University Veterinary Hospital 0situated in Perth and the Brookton Veterinary Hospital (BVH), a rural practice in the south-west of the State. The records were examined for cases of chemical, animal and plant poisonings in the period from 1978 to 1990. At MUVH during this time 158poisoning cases in dogs (0.86% of a total of 18455 cases) and 36 cases in cats (0.76% of a total of 4748 cases) were diagnosed. From the records of the BVH, 156 cases of poisonings in dogs and 14 cases in cats were identified. The diagnosisof poisoning was made on at least one of the following criteria: the isolation of the poison; clinical signs; necropsy; the presence of poison in emetic samples; observationsf envenomation or consumptionof the toxin. The data were clssified on type of poison, season of occurrence, sex, age and breedof animal and survival rate. Poisonings due to adversereactions to medications were not included in this study. In this survey 81.5% of the poisoning cases were dogs, which is similar to the 78% recorded in an urban practice in Melboume (Studdert 1985a). The ratio of poisoned dogs to cats (4.4:l) was similar to the ratio of dogs to cats for all casapresented at MUVH (3.91), but dogs were over-repmmted when compared with the generalpetpopulationinPerth,wherethedog-tocat,ratiois1.1 to 1 (Robertson et al1990). The low numbers of poison& cats seen at both practices may be associated with dogs having greater access and exposure to poisons. Unfortunately the small number of cats limits the conclusions that can be made about this population. The survival rate for poisoned dogs was similar between the practices; however, significantly more cats presented to MUVH survived (Table 1). The case fatality rate for dogs and cats at MUVH was lower than the 19.4% and 28.1%. respectively, 194
Rural’
Urban+
(“w
(“/.I ~~
Dogs Survival Natural death Euthanasia
Cats Survival Natural death Euthanasia
89
6.5 4.5
~
~
86 8
6
57
97
36 7
3 0
Brookton Veterinary Hospital Murdoch University Veterinary Hospital
reported by Studdert (1985a) in Melbourne, but similar to the 12% reported for dogs in the USA (Osweiler 1983). These differences may arise because of the different type of agents associated with poisonings in the localities. The sex specific rates of poisoning for dogs and cats were similar for both practices. Neutering did not influence the prevalence of poisoning. These findings agree with those of Osweiler (1983), but Studdert (1985b) reported a slightly higher prevalence of poisoning with snail baits in bitches. Analysis of the age distribution showed that 30% of poisoned dogs at MUVH and 23% at BVH were less than 1yr of age. When the age structure of the general dog population was considered (Robertsonef d1990), dogs less than 1 yr of age were 2.4 times over-represented in the poisoning survey. Studdert (1985a, b), when investigating poisoning of dogs with snail baits, reported similar proportions in this age group. Similarly, Osweiler (1983) reported that dogs less than 2 yr old were more likely to be affected with poisonings, and Prescott (1983) reported a mean age of 8 mo for poisoned dogs in Brisbane. With poisoned cats, 17% and 28% were less than 1 yr old at MUVH and BVH respectively.The proportion of cats in this age group was similar to that reportedfor thegeneral catpopulationinPerth (Robertson et d 1990). Table 2 records the frequency of specific poisonings in the practices. Molluscicides accounted for 25% of the poisonings in dogs in Perth (MUVH) but only 11% from the rural practice (BVH). Studdert (1985a, b) reported similar findings with 31% of all poisonings in Melboume being due to molluscicides. Organophosphorus compounds (OP) were the most frequent agent to cause poisonings at BVH in both dogs and cats (35 and 36%, respectively). This compared with 6% and 22% at MLJVH. The difference for dogs is probably due to their greater access to OPs in rural environments. These compounds were commonly used for vertebrate pest control and control of ectoparasites in production animals in rural environments during the period of study. Similarly, poisoning with strychnine was more frequent in rural areas (14%), where it also is used for vermin control. In both dogs and cats rodenticide toxicity was more common at BVH than at MSJVH. This may be associated with the greater problem of rodents in a rural environment. Quick (1982) similarly reported that rodenticide toxicity in dogs accounted for 45% of poisoning cases from rural areas in the UK, but OPs represented only 13% of his cases. Blakley (1984) reported that strychnine accounted for 92% of poisonings in dogs in Canada, highlighting the differences between countries. Prescott (1983) found that lead was the major poison (43%) affecting dogs in Brisbane. with strychnine responsible for 21% of the cases. The
Australian Veterinary Journal Vol69, No 8 August 1992
TABLE 2 Poisonlngsdiagnoaed In dogs and cats In a rural and an urban practice in the period from 1978 to 1990 Type of
poison Insecticides Organophosphorus compounds Chlorinated hydrocarbons Mammalicides Anticoagulant rodenticides Strychnine 1080 Miscellaneous Arsenic Glycols, phenols Lead Others Plant Molluscicides Metaldehyde Carbarnates Unidentified
Dogs
Cats
Rural’ No. (“h)
Urbant No. (“h)
Aural’ NO.(%)
Urbant NO.(%)
55 (35.3)
9 (5.7)
5 (35.7) l(7.1)
O(2.2)
6 (42.9)
2(5.6)
32 (20.5) 22 (14.1) 2 (1.3)
12 (7.6) 6 (3.8)
l(7.1)
6 (3.9) 6 (3.9)
1 1 (7.1) 6 (3.9) 16 (10.3)
Zootoxins Snake bite Wasp, bee, ant
6 (3.8) 1 (0.6) 7 (4.4) 12 (7.6)
2(5.6) i(2.8) l(2.8) l(2.8)
20 (1 2.6) 20 (1 2.6) 33 (20.8)
2(5.6) l(7.1)
17 (10.7) 15 (9.4)
7(9.4) 9(25) 3(8.3)
~~~
Total cases +
156
158
14
36
Brookton Veterinary Hospital Murdoch University Veterinary Hospital
differences between the relative importance of specific poisons in Brisbane, Melbourne and Perth may be associated with different levels of usage between the cities and changes in the usage of chemicals over time. Osweiler (1983)also reported variation in the importance of specific poisonings and envenomations between regions of the USA. Unexpectedly,snake bites were more common at MUVH (1 1% of dogs and 25% of cats) than BVH. This may be associated with the corridors of bushland in suburban Perth. which provide a suitableenvironmentfor snakes to come in contact withpets. The problems of finding envenomed pets in the country, greater distance from veterinary servicesand variation in the distribution of snakes may also be factors in the BVH figures. Overall, slightly more cases of poisonings occurred in spring, although for dogs there were no significant differences between the number of cases presented in each season For individual poisons there was some seasonal variation, with 69% of snake bites occurring in spring and summer. Blakley (1984)found significant seasonal effects of poisonings with lead, chlorinated hydrocarbons and strychnine. In the current survey 47% of all cat poisonings occurred during the spring months. Forty-four percent of poisoned dogs at MUVH were crossbreds. When this was compared with all the dogs examined at MUVH, crossbreds were 36times over-represented.This could lead to the belief that crossbreds are more at risk from poisoning than pure bred dogs. However, when the proportion of crossbred dogs poisoned was comparedwith the general dog population in Perth (Robertsonef a1 1990)these dogs were represented in about the same proportion as for the general population. Osweiler (1983) found that specific breeds (such as Pointers. Dachshunds and Beagles) were more likely to present with poisonings than crossbreds, however these proportions were not related back to
Australian VeterinaryJournal Vol69, No 8 August 1992
the general dog population. Prescott (1983)found that dogs with short coats were over-represented in his study of cases of lead poisoning. These differences show the importance of having data specific for the general population. Sixty-nine percent of cats presented to MUVH for poisonings were crossbreds. Persian and Burmese cats were over-represented by 4 and 2.8 times, respectively, when compared with the general cat population. If practitioners are aware of the poisons commonly affecting local dogs and cats, they can ensure that the necessary drugs and antidotes are kept in their practice, and this increased awareness may lead to a reduction in the case fatality rate for poisonings. This survey shows that in an urban practice poisoning with molluscicides is more likely, while in rural practice poisoning with organophosphosphorus compounds, rodenticides and strychnine is more likely. There appear to be no sex and breed predispositionsto poisonings; however, young animals are more likely to be poisoned, particularly in the spring and summer months. This project was funded by a grant from the Murdoch University Foundation for Companion Animals.
References Blakley BR (1984) Can VefJ25: 17 Osweiler GD (1983) In Cwrent Veterinary Therapy, edited by Kirk RW, 8th edn, Saunders, Philadelphia, p 76 Prescott CW (1983) Ausf Vet J 60: 270 Quick M p (1982) Vet Rec 111: 5 Robertson ID,Edwards JR,Shaw SE and Clark WT (1990) Ausf Vet Pracf 20: 210 Studded VP (1985a)Aust Vet J 62: 133 Studded VP (1985b)Aust Vet J62: 269 (Acceptedfor publication 29 April 1992)
195
SHORT CONTRIBUTIONS
A retrospective study of poisoning cases in dogs and cats: comparisons between a rural and an urban practice School of Veterinary Studies, Murdoch University, Murdoch, Western Australia 6150
ID ROBERTSON
Brookton Veterinary Hospital. Box 84, Brookton, Western Australia 6306
M LEGGOE
School of Veterinary Studies, Murdoch University, Murdoch, Western Australia 6150
PR DORLING SE SHAW WT CLARK
Poisoned dogs and cats often require emergency treatment by aveterinary practitioner. Ifpractitioners areawareofthoseagents commonly associated with poisonings in their locality, diagnosis may be achieved more rapidly enabling prompt treatment to be instigated to improve the animal’s chance of survival and reduce the anguish of the owner. The relative importance of specific poisons may vary in different geographic regions, depending on such factors as the type of pesticides commonly used, the flora and fauna present in the regions, the different practices in handling and housing domestic pets, and the population density of the exposed species (Studdert 1 9 8 5 Osweiler ~ 1983). There is little information available on the prevalence of specific poisonings in dogs and cats in Western Australia. A retrospective study was undertaken using computerised records from 2 sources, namely, the Murdoch University Veterinary Hospital 0situated in Perth and the Brookton Veterinary Hospital (BVH), a rural practice in the south-west of the State. The records were examined for cases of chemical, animal and plant poisonings in the period from 1978 to 1990. At MUVH during this time 158poisoning cases in dogs (0.86% of a total of 18455 cases) and 36 cases in cats (0.76% of a total of 4748 cases) were diagnosed. From the records of the BVH, 156 cases of poisonings in dogs and 14 cases in cats were identified. The diagnosisof poisoning was made on at least one of the following criteria: the isolation of the poison; clinical signs; necropsy; the presence of poison in emetic samples; observationsf envenomation or consumptionof the toxin. The data were clssified on type of poison, season of occurrence, sex, age and breedof animal and survival rate. Poisonings due to adversereactions to medications were not included in this study. In this survey 81.5% of the poisoning cases were dogs, which is similar to the 78% recorded in an urban practice in Melboume (Studdert 1985a). The ratio of poisoned dogs to cats (4.4:l) was similar to the ratio of dogs to cats for all casapresented at MUVH (3.91), but dogs were over-repmmted when compared with the generalpetpopulationinPerth,wherethedog-tocat,ratiois1.1 to 1 (Robertson et al1990). The low numbers of poison& cats seen at both practices may be associated with dogs having greater access and exposure to poisons. Unfortunately the small number of cats limits the conclusions that can be made about this population. The survival rate for poisoned dogs was similar between the practices; however, significantly more cats presented to MUVH survived (Table 1). The case fatality rate for dogs and cats at MUVH was lower than the 19.4% and 28.1%. respectively, 194
Rural’
Urban+
(“w
(“/.I ~~
Dogs Survival Natural death Euthanasia
Cats Survival Natural death Euthanasia
89
6.5 4.5
~
~
86 8
6
57
97
36 7
3 0
Brookton Veterinary Hospital Murdoch University Veterinary Hospital
reported by Studdert (1985a) in Melbourne, but similar to the 12% reported for dogs in the USA (Osweiler 1983). These differences may arise because of the different type of agents associated with poisonings in the localities. The sex specific rates of poisoning for dogs and cats were similar for both practices. Neutering did not influence the prevalence of poisoning. These findings agree with those of Osweiler (1983), but Studdert (1985b) reported a slightly higher prevalence of poisoning with snail baits in bitches. Analysis of the age distribution showed that 30% of poisoned dogs at MUVH and 23% at BVH were less than 1yr of age. When the age structure of the general dog population was considered (Robertsonef d1990), dogs less than 1 yr of age were 2.4 times over-represented in the poisoning survey. Studdert (1985a, b), when investigating poisoning of dogs with snail baits, reported similar proportions in this age group. Similarly, Osweiler (1983) reported that dogs less than 2 yr old were more likely to be affected with poisonings, and Prescott (1983) reported a mean age of 8 mo for poisoned dogs in Brisbane. With poisoned cats, 17% and 28% were less than 1 yr old at MUVH and BVH respectively.The proportion of cats in this age group was similar to that reportedfor thegeneral catpopulationinPerth (Robertson et d 1990). Table 2 records the frequency of specific poisonings in the practices. Molluscicides accounted for 25% of the poisonings in dogs in Perth (MUVH) but only 11% from the rural practice (BVH). Studdert (1985a, b) reported similar findings with 31% of all poisonings in Melboume being due to molluscicides. Organophosphorus compounds (OP) were the most frequent agent to cause poisonings at BVH in both dogs and cats (35 and 36%, respectively). This compared with 6% and 22% at MLJVH. The difference for dogs is probably due to their greater access to OPs in rural environments. These compounds were commonly used for vertebrate pest control and control of ectoparasites in production animals in rural environments during the period of study. Similarly, poisoning with strychnine was more frequent in rural areas (14%), where it also is used for vermin control. In both dogs and cats rodenticide toxicity was more common at BVH than at MSJVH. This may be associated with the greater problem of rodents in a rural environment. Quick (1982) similarly reported that rodenticide toxicity in dogs accounted for 45% of poisoning cases from rural areas in the UK, but OPs represented only 13% of his cases. Blakley (1984) reported that strychnine accounted for 92% of poisonings in dogs in Canada, highlighting the differences between countries. Prescott (1983) found that lead was the major poison (43%) affecting dogs in Brisbane. with strychnine responsible for 21% of the cases. The
Australian Veterinary Journal Vol69, No 8 August 1992
TABLE 2 Poisonlngsdiagnoaed In dogs and cats In a rural and an urban practice in the period from 1978 to 1990 Type of
poison Insecticides Organophosphorus compounds Chlorinated hydrocarbons Mammalicides Anticoagulant rodenticides Strychnine 1080 Miscellaneous Arsenic Glycols, phenols Lead Others Plant Molluscicides Metaldehyde Carbarnates Unidentified
Dogs
Cats
Rural’ No. (“h)
Urbant No. (“h)
Aural’ NO.(%)
Urbant NO.(%)
55 (35.3)
9 (5.7)
5 (35.7) l(7.1)
O(2.2)
6 (42.9)
2(5.6)
32 (20.5) 22 (14.1) 2 (1.3)
12 (7.6) 6 (3.8)
l(7.1)
6 (3.9) 6 (3.9)
1 1 (7.1) 6 (3.9) 16 (10.3)
Zootoxins Snake bite Wasp, bee, ant
6 (3.8) 1 (0.6) 7 (4.4) 12 (7.6)
2(5.6) i(2.8) l(2.8) l(2.8)
20 (1 2.6) 20 (1 2.6) 33 (20.8)
2(5.6) l(7.1)
17 (10.7) 15 (9.4)
7(9.4) 9(25) 3(8.3)
~~~
Total cases +
156
158
14
36
Brookton Veterinary Hospital Murdoch University Veterinary Hospital
differences between the relative importance of specific poisons in Brisbane, Melbourne and Perth may be associated with different levels of usage between the cities and changes in the usage of chemicals over time. Osweiler (1983)also reported variation in the importance of specific poisonings and envenomations between regions of the USA. Unexpectedly,snake bites were more common at MUVH (1 1% of dogs and 25% of cats) than BVH. This may be associated with the corridors of bushland in suburban Perth. which provide a suitableenvironmentfor snakes to come in contact withpets. The problems of finding envenomed pets in the country, greater distance from veterinary servicesand variation in the distribution of snakes may also be factors in the BVH figures. Overall, slightly more cases of poisonings occurred in spring, although for dogs there were no significant differences between the number of cases presented in each season For individual poisons there was some seasonal variation, with 69% of snake bites occurring in spring and summer. Blakley (1984)found significant seasonal effects of poisonings with lead, chlorinated hydrocarbons and strychnine. In the current survey 47% of all cat poisonings occurred during the spring months. Forty-four percent of poisoned dogs at MUVH were crossbreds. When this was compared with all the dogs examined at MUVH, crossbreds were 36times over-represented.This could lead to the belief that crossbreds are more at risk from poisoning than pure bred dogs. However, when the proportion of crossbred dogs poisoned was comparedwith the general dog population in Perth (Robertsonef a1 1990)these dogs were represented in about the same proportion as for the general population. Osweiler (1983) found that specific breeds (such as Pointers. Dachshunds and Beagles) were more likely to present with poisonings than crossbreds, however these proportions were not related back to
Australian VeterinaryJournal Vol69, No 8 August 1992
the general dog population. Prescott (1983)found that dogs with short coats were over-represented in his study of cases of lead poisoning. These differences show the importance of having data specific for the general population. Sixty-nine percent of cats presented to MUVH for poisonings were crossbreds. Persian and Burmese cats were over-represented by 4 and 2.8 times, respectively, when compared with the general cat population. If practitioners are aware of the poisons commonly affecting local dogs and cats, they can ensure that the necessary drugs and antidotes are kept in their practice, and this increased awareness may lead to a reduction in the case fatality rate for poisonings. This survey shows that in an urban practice poisoning with molluscicides is more likely, while in rural practice poisoning with organophosphosphorus compounds, rodenticides and strychnine is more likely. There appear to be no sex and breed predispositionsto poisonings; however, young animals are more likely to be poisoned, particularly in the spring and summer months. This project was funded by a grant from the Murdoch University Foundation for Companion Animals.
References Blakley BR (1984) Can VefJ25: 17 Osweiler GD (1983) In Cwrent Veterinary Therapy, edited by Kirk RW, 8th edn, Saunders, Philadelphia, p 76 Prescott CW (1983) Ausf Vet J 60: 270 Quick M p (1982) Vet Rec 111: 5 Robertson ID,Edwards JR,Shaw SE and Clark WT (1990) Ausf Vet Pracf 20: 210 Studded VP (1985a)Aust Vet J 62: 133 Studded VP (1985b)Aust Vet J62: 269 (Acceptedfor publication 29 April 1992)
195
