In 2000, a Los Angeles woman was arrested on suspicion of animal cruelty after more than 600 animals, mostly dogs and cats, were found in her tiny home. Conditions were filthy and so crowded there was barely room to move.

You’ve probably read such stories time and time again, from cities around the world, from rich places and poor ones. You may have lived next door to such a person. The phenomenon of pet hoarders is common enough that I suspect it may be a unique psychiatric condition. Yet, it has not been recognised as such. If you press a psychiatric professional, he or she will most likely think it falls under some kind of obsessive-compulsive disorder. There is certainly very little actual psychiatric literature on the subject. Should we care, besides for it being a quirk of human nature?

We should. For one thing, many if not most serious pet hoarders need professional help, according to Hong Kong-based private psychologist Agnes Lai. For another, through their misguided attachment or even love for their animals, they actually cause them prolonged suffering. So the problem is clearly of interest to animal welfare groups and government departments.

At the stage of intervention, it’s not unusual to find some of the animals already dead and others seriously ill. Yet, hoarders almost inevitably insist their animals have been well cared for and that their homes are clean, despite clear evidence to the contrary. They are in a state of denial.

Social isolation is a common factor, though this may be the result of their behaviour rather than the cause of it. Trouble with neighbours is almost a given, as those living close by tend to have made repeated complaints, usually first to their own building management and then to the authorities.

Hoarders’ homes often have inadequate or no utilities such as phone and internet connection, air conditioning, flushing toilets, refrigeration and cooking facilities.

Many think of themselves as parents to their animals and so are extremely reluctant to let other people take care of or remove them. Offers by well-wishers to adopt animals are often refused.

One American study in 1999 defined an animal hoarder as “someone who accumulates a large number of animals; fails to provide minimal standards of nutrition, sanitation and veterinary care; and fails to act on the deteriorating condition of the animals (including disease, starvation and even death) or the environment (severely overcrowded and unsanitary conditions), or the negative impact of the collection on their own health and well-being.”

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Such cases may drag on for a long time, as hygiene conditions deteriorate so badly as to affect the neighbours. Many hoarders simply refuse to cooperate over a long period, leading to final intervention by the police. Some end up in court and face jail. But if government agents and animal welfare advocates were trained to recognise and deal with such cases, early intervention could make life easier for everyone – the hoarder, the animals and the neighbours.

Tracy Yau is a Hong Kong-based writer and journalist