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The hazards of pet ownership
Cross-talk
The hazards of pet ownership Investigators of puzzling infections may have to quiz their patients about several potentially relevant matters: from recent travels and food consumed, to sexual encounters and occupational exposures. A recent case suggests that they might usefully include hobbies too, especially when dealing with pet owners. The case was that of a young woman who developed an infection apparently contracted from a wild rat she kept at home. The team of doctors and veterinarians reporting the incident (Vet Rec 2009; 164: 186) conclude, in light of both her experience and theirs, that “the practice of adopting feral rats should be actively discouraged”. The verminous creature, which caused the trouble in this instance, was thought to have been a pet rat that had escaped and become semiferal. The woman had owned two previous rats, one of which had recently been killed after developing a chronic, intractable respiratory disease. She adopted the new one when a neighbour’s cat brought it into the house. The rat fancier was admitted to hospital after a week of lethargy, generalised myalgia, abdominal pain, and other symptoms. She then became much worse, developed acute renal failure, and was transferred to intensive care. Fortunately, following the diagnosis and treatment of leptospirosis, she recovered completely. Detection of leptospiral DNA in the rat’s kidney indicated the virtually certain origin of the woman’s infection. “Wild rats are a well-documented source of human infection with Leptospira interrogans serogroup icterohaemorrhagiae”, the authors write. They continue, “the risk of acquiring zoonotic diseases, such as leptospirosis or salmonellosis, directly from feral rats or via pet rats that have contact with wild rats, should not be underestimated”. There are probably many more hobbyists hovering around fish tanks than there are rat fanciers. But that does not mean that they, or their general practitioners, are any more aware of microbial hazards accompanying their otherwise canny pastime. When four cases of “fish tank granuloma” caused by Mycobacterium marinum came to light in Bristol some years ago, the investigators found that none of the men affected were aware that their piscine pursuit could lead to skin infection (BMJ 1990; 300: 1069–70). One victim was a 36-year-old shop fitter who cut his thumb while cleaning his tank. The wound failed to heal despite the use of oral flucloxacillin, and over the next year it developed into a painful red plaque that discharged pus from time to time. Only when the patient was referred to a dermatologist did the correct diagnosis become apparent. Biopsy material yielded M marinum,
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and the lesion improved rapidly after a 6-week course of co-trimoxazole. Although well known to dermatologists, this type of infection is much less familiar to non-specialists— especially fish fanciers. When the investigators contacted members of three tropical fish clubs in Bristol, less than a third of respondents were aware of the risks involved in their hobby. While many were conscious of a “wasting disease” in fish (actually a form of tuberculosis caused by M marinum) they did not know that the organism could invade human tissues. A third reason why pathological sleuths might inquire about their patients’ hobbies is that they can interfere with diagnostic investigations. One example (BMJ 2003; 326: 541–42) concerned a woman with perplexingly high fasting levels of gut hormones. These came to light originally during investigation of her irritable-bowel syndrome and remained high for many years afterwards, although CT scans were always normal. The woman was eventually booked for pancreatic angiography with calcium stimulation, to ascertain whether she had abnormally functioning islet cells. Then it occurred to the investigators that their patient might have heterophilic antibodies that could interfere with radioimmunoassays based on rabbit antibodies. Simply by adding non-immune rabbit serum to the gastrin assay buffer, they confirmed that this was indeed so. And, on questioning, the woman explained proudly that she did indeed keep rabbits—as many as 80 at one time. The angiography was cancelled.
Bernard Dixon 130 Cornwall Road, Ruislip Manor, Middlesex, HA4 6AW, UK; [email protected]
www.thelancet.com/infection Vol 9 May 2009
The hazards of pet ownership Investigators of puzzling infections may have to quiz their patients about several potentially relevant matters: from recent travels and food consumed, to sexual encounters and occupational exposures. A recent case suggests that they might usefully include hobbies too, especially when dealing with pet owners. The case was that of a young woman who developed an infection apparently contracted from a wild rat she kept at home. The team of doctors and veterinarians reporting the incident (Vet Rec 2009; 164: 186) conclude, in light of both her experience and theirs, that “the practice of adopting feral rats should be actively discouraged”. The verminous creature, which caused the trouble in this instance, was thought to have been a pet rat that had escaped and become semiferal. The woman had owned two previous rats, one of which had recently been killed after developing a chronic, intractable respiratory disease. She adopted the new one when a neighbour’s cat brought it into the house. The rat fancier was admitted to hospital after a week of lethargy, generalised myalgia, abdominal pain, and other symptoms. She then became much worse, developed acute renal failure, and was transferred to intensive care. Fortunately, following the diagnosis and treatment of leptospirosis, she recovered completely. Detection of leptospiral DNA in the rat’s kidney indicated the virtually certain origin of the woman’s infection. “Wild rats are a well-documented source of human infection with Leptospira interrogans serogroup icterohaemorrhagiae”, the authors write. They continue, “the risk of acquiring zoonotic diseases, such as leptospirosis or salmonellosis, directly from feral rats or via pet rats that have contact with wild rats, should not be underestimated”. There are probably many more hobbyists hovering around fish tanks than there are rat fanciers. But that does not mean that they, or their general practitioners, are any more aware of microbial hazards accompanying their otherwise canny pastime. When four cases of “fish tank granuloma” caused by Mycobacterium marinum came to light in Bristol some years ago, the investigators found that none of the men affected were aware that their piscine pursuit could lead to skin infection (BMJ 1990; 300: 1069–70). One victim was a 36-year-old shop fitter who cut his thumb while cleaning his tank. The wound failed to heal despite the use of oral flucloxacillin, and over the next year it developed into a painful red plaque that discharged pus from time to time. Only when the patient was referred to a dermatologist did the correct diagnosis become apparent. Biopsy material yielded M marinum,
272
and the lesion improved rapidly after a 6-week course of co-trimoxazole. Although well known to dermatologists, this type of infection is much less familiar to non-specialists— especially fish fanciers. When the investigators contacted members of three tropical fish clubs in Bristol, less than a third of respondents were aware of the risks involved in their hobby. While many were conscious of a “wasting disease” in fish (actually a form of tuberculosis caused by M marinum) they did not know that the organism could invade human tissues. A third reason why pathological sleuths might inquire about their patients’ hobbies is that they can interfere with diagnostic investigations. One example (BMJ 2003; 326: 541–42) concerned a woman with perplexingly high fasting levels of gut hormones. These came to light originally during investigation of her irritable-bowel syndrome and remained high for many years afterwards, although CT scans were always normal. The woman was eventually booked for pancreatic angiography with calcium stimulation, to ascertain whether she had abnormally functioning islet cells. Then it occurred to the investigators that their patient might have heterophilic antibodies that could interfere with radioimmunoassays based on rabbit antibodies. Simply by adding non-immune rabbit serum to the gastrin assay buffer, they confirmed that this was indeed so. And, on questioning, the woman explained proudly that she did indeed keep rabbits—as many as 80 at one time. The angiography was cancelled.
Bernard Dixon 130 Cornwall Road, Ruislip Manor, Middlesex, HA4 6AW, UK; [email protected]
www.thelancet.com/infection Vol 9 May 2009