Introduction

Animal hoarding is a public health issue that exists in every community around the world and has the serious potential of damaging human and animal welfare.¹ The definition of animal hoarding is a situation in which a person’s household contains more animals than the person in charge of the household can provide adequate care for.¹ Causes of animal hoarding range from malicious intent to psychiatric delusions, and identification of animal hoarding cases often requires the involvement of an interdisciplinary team or task force.² Animal hoarding is a cross-cultural phenomenon that has been documented in communities around the world.^3–8 However, there is some evidence of geographic differences in the consequences of animal hoarding: animal hoarding tends to be more severe in nature in a rural context,⁶ likely due to decreased visibility of the problem. Furthermore, despite the documented consequences of having an excessive number of animals in the home, there is a lack of quantitative knowledge on patterns of normative animal ownership, particularly in a rural setting.

Animals living in a hoarded household are typically in poor health and not able to receive essential food, water, and shelter. Furthermore, these animals can pose a health risk to other animals and humans in the community, including through exposure to zoonotic diseases^9–11 and insect infestations.³ However, the link between animal hoarding and human disease is not universally detected; at least 1 case study⁴ found no link between animal hoarding in Brazil and presence of zoonotic diseases in human owners, underlining the need to understand the full range of the presentation of animal hoarding in the community. Animals recovered from houses where animal hoarding was present frequently require veterinary care due to neglect,^5,12 but many veterinary professionals may not have adequate training, information, and parameters to assess whether the pet owner may be engaging in animal hoarding. Thus, it is critical to investigate possible parameters for animal hoarding, including numbers of pets per household and health conditions of those pets for veterinary and related health professionals to preserve the human-animal bond and protect human clients and animal patients from these conditions.

Currently, animal hoarding is considered a subtype of hoarding disorder¹³; however, there is growing evidence that animal hoarding and object hoarding are distinct conditions rather than variations of the same disorder.^5,14,15 Evidence of object hoarding is only detected in approximately half of animal hoarding cases,^5,14,16 and animal hoarding is rare in individuals presenting for treatment for object hoarding.¹⁵ Furthermore, the clutter accumulated in cases of animal hoarding is a typical byproduct of the lack of care of animals than objects retained due to sentimental or intrinsic value.¹⁷ Animal hoarding as a distinct disorder has been proposed as having parallel criteria to object hoarding: individuals would be required to have accumulated more animals than they can properly care for, have difficulty giving away animals, and demonstrate impairment in daily functioning (eg, the individual experiences impairment in social activities, work performance, and managing their finances).¹⁴

The most hoarded animals are cats, dogs, and rabbits,^{1,3,6,9,18,19} although equine hoarding has also been reported in more rural areas.^7,16,19 Individuals with animal hoarding problems often lack insight into the conditions of the animals, frequently believing they are acting altruistically and rescuing the very animals they then neglect.^1,5 Most animal hoarding cases are unintentional, with only 10% of cases involving individuals who intentionally exploit animals.⁶ Unintentional animal hoarding can occur for a variety of reasons, including when formerly responsible pet owners are no longer able to prevent indiscriminate breeding due to physical or cognitive decline of the person (30% of cases).^6,7 Specifically, animal hoarding has been linked to executive dysfunction in the owner, most notably deficits with abstract verbal reasoning.¹⁸

Unintentional animal hoarding can also occur as consequence of an underlying psychological condition. Although the prevalence of psychiatric diagnoses in cases of animal hoarding has not been systematically examined, evidence from a study¹⁶ in Australia suggests that psychiatric diagnoses, either diagnosed officially or suspected, may be present in over two-thirds of animal hoarding cases. Animal hoarding due to mental health issues (either as a symptom of another psychological disorder or as a standalone diagnosis) is often further differentiated by reasons endorsed by the individuals for hoarding animals, including being an “overwhelmed caregiver” (24% of cases) or a “rescuer” (22%) and “loving animals” (14%).⁶

The above summary of the literature illustrates the nascent nature of research on animal hoarding. To better understand the etiology and consequences of animal hoarding, a sense of normative animal ownership patterns is needed. Thus, the primary purpose of this study was to conduct a retrospective review of veterinary medical records from a university-based community clinic in Mississippi to determine patterns of animal ownership in a rural setting and possible health-care–based indicators of animal hoarding. We hypothesized that increased numbers of animals would be associated with decreased positive indicators of animal care (eg, number of clinic visits, spay/neuter status, annual checkup, dental visit, and vaccine count) and increased negative indicators of animal health (eg, total physical problems recorded as well as problems specifically noted for skin, hydration, and mammary glands). Finally, we had an exploratory aim to provide preliminary estimates of the prevalence of possible animal hoarding in rural Mississippi.

Materials and Methods

Study procedures were determined to be exempt from review by the Mississippi State University (MSU) institutional review board and IACUC. Records from the MSU College of Veterinary Medicine Community Veterinary Services from 2009 to 2019 were reviewed. The records from all owners who reported having animals that interacted with 8 or more other animals on average were reviewed by hand. The senior author, a veterinarian at the MSU College of Veterinary Medicine, hand-coded cases/owners she knew to be from legitimate rescues, shelters, or privately owned veterinary clinics/practices, and the associated data were subsequently removed. Across the study period, 28,446 unique encounters occurred among 8,331 unique animals and 6,440 unique owners. Animal species included canine, feline, avian, rodent, reptile, and other small-animal exotics (eg, rabbit). Animals and owners were cross classified such that a specific animal often had multiple owners and a specific owner often had multiple animals seen in the clinic across the study period. An open-text metric of other animals with regular interactions was collected at intake and manually entered. We coded this to indicate the average number of other animals cohabitating reported at the time of the encounter, including removing animals from the count that were obviously from a different household or were livestock. This measure was averaged across all encounters to create an average number of animals in a household. Animals were then grouped into 3 categories on the basis of the total number of animals in each household (1 to 3 animals, 4 to 7, and ≥ 8). Group cutoffs were established de novo on the basis of the clinical judgment of the senior author.

Indicators of care for canine and feline animals were taken from values indicated on the physical examination in the record. Due to the retrospective nature of the study, analyses were limited to what factors were available within the database; a few general health indicators were selected to represent overall health care of the animals in this study. For positive indicators of animal care, we examined number of clinic visits, reproductive status (spayed/neutered), presence of at least 1 annual checkup, presence of at least 1 dental visit, and number of vaccines. These selections for indicators of animal care were made due to assumptions about likely correlates of routine veterinary care (eg, dental visit). For negative indicators of animal care, we examined the percentage of cases with problems related to skin, hydration, and mammary glands. Specifically, reported abnormal results for skin, mammary glands, and hydration were collapsed to indicate the proportion of episodes in which these issues were noted. These selections for indicators of animal health were made on the basis of what problems are likely to arise for animals living in a hoarded house based on the clinical judgment of the senior author. The presence of skin problems was selected as an indicator because dermatologic disease is common in pets with external parasites and poor environmental conditions, which is not uncommon in hoarded houses. Animals in a house that is overcrowded with other animals may not have regular access to clean water, leading to dehydration. Finally, animal hoarding related to indiscriminate breeding may lead to problems with mammary glands in the animals. In general, animals that are not spayed or neutered may also have increased incidence of mammary issues, and animals in hoarded situations may be less likely to be spayed or neutered. Additionally, the total number of physical results indicated as abnormal was averaged across all episodes to provide a global appraisal of the health of the animal.

Indicators of veterinary care were determined from the reason for visits, which were manually entered. Reasons including the words “dental” or “teeth” and “clean” together were used to indicate a dental visit. Reasons including the terms “annual,” “checkup,” or “check-up” were used to indicate an annual checkup. These 2 indicators were collapsed across encounters to indicate whether an animal had ever been seen for a dental or checkup visit, respectively. A vaccination database of all vaccines received at the clinic was used to establish the total number of vaccines given to an animal. Finally, reproductive status was manually entered with inclusion of the words “spayed,” “neutered,” or “OHE” indicating a spayed/neutered animal. If more than half of visits indicated a spayed/neutered animal it was assumed to be spayed/neutered, otherwise it was assumed to be intact.

Results

Between 2009 and 2019, animals seen in the clinic (ie, dogs, cats, and other small animals) generally had 1 to 2 individuals listed as their owners (mean, 1.43; SD, 0.84; range, 1 to 11) and owners typically had more than 1 pet seen in the clinic (mean, 1.85; SD, 2.97; range, 1 to 99). Of 6,440 owners, 68.7% (4,424/6,440) had only 1 animal seen in the clinic, 21.8% (1,403/6,440) had 2 to 3 animals seen in the clinic, and 1.4% (88/6,440) of owners had 8 or more animals seen in the clinic. Separate from animals that were seen in the clinic, owners also reported total number of animals in the household (ie, including both animals seen in the clinic and animals not seen in the clinic). Owners reported an average of 1 to 2 animals in a household (mean, 1.51; SD, 2.70; range, 1 to 85). Nearly half (46.9% [3,903/8,331]) of owners reported that the animal being seen in the clinic was the only pet in the household, with an additional 35.9% (2,989/8,331) reporting that the animal was 1 of 2 or 3 animals in a home. Finally, 2.1% (177/8,331) of animals lived in a household with 8 or more animals.

Most animals seen in the clinic were canine (73.3% [6,105/8,331]) and feline (23.3% [1,941/8,331]). Most canine cases were from a household with an average of 3 or fewer animals (81.6% [4,979/6,105]), followed by households with an average of 4 to 7 animals (16.0% [977/6,105]) and households with an average of 8 or more animals (2.4% [149/6,105]). Most feline cases were from a household with an average of 3 or fewer animals (70.6% [1,370/1,941]), followed by households with an average of 4 to 7 animals (25.1% [488/1,941]) and households with an average 8 or more animals (4.3% [83/1,941]).

The indicators of health separated by self-reported number of animals for canines and felines are summarized (Tables 1 and 2). Follow-up testing focused on the differences found between households with ≥ 8 animals and households with < 8 animals. Among canines, animals from households with ≥ 8 animals had fewer visits (2.36 vs 3.97 [4 to 7 animals] and 3.73 [1 to 3 animals]), fewer vaccinations (1.30 vs 3.63 [4 to 7 animals] and 2.83 [1 to 3 animals]), more skin problems (34.17 vs 25.25 [4 to 7 animals] and 21.61 [1 to 3 animals]), more mammary gland problems (3.58 vs 1.66 [4 to 7 animals] and 0.60 [1 to 3 animals]), and more overall problems (2.76 vs 1.95 [4 to 7 animals] and 2.08 [1 to 3 animals]) than animals from households with 1 to 3 animals and households with 4 to 7 animals (P < .05 for all comparisons). Compared to canines from households with 4 to 7 animals, canines from households with ≥ 8 animals were less likely to be spayed/neutered (39.6% vs 57.4%) or have had an annual checkup (12.1% vs 20.6%; P < .05 for all comparisons) but were not significantly different than canines from households with 1 to 3 animals. Dental visits among canines from households with ≥ 8 animals were not significantly different than households with 1 to 3 animals or households with 4 to 7 animals (P > .05 for all comparisons).

Among felines, animals from households with ≥ 8 animals were more likely to have mammary gland problems (1.81% vs 0.25% [4 to 7 animals] and 0.34% [1 to 3 animals]) and had more overall problems (2.22 vs 1.69 [4 to 7 animals] and 1.59 [1 to 3 animals]) than animals from households with 1 to 3 animals and households with 4 to 7 animals (P > .05 for all comparisons). Felines from households with ≥ 8 animals were more likely to have skin problems than felines from households with 1 to 3 animals (26.50% vs 17.22%; P = .05) but not from households with 4 to 7 animals (20.90%; P > .05). There were several indicators for which the households with 4 to 7 animals demonstrated increased animal care, as follows: felines from households with 4 to 7 animals were more likely to be spayed/neutered than felines from households of ≥ 8 animals (65.4% vs 53.0%) or felines from households with 1 to 3 animals (52.3%; P < .001). Felines from households with 4 to 7 animals were also more likely to have had a dental visit than felines from households of ≥ 8 animals (14.1% vs 9.6%) or felines from households with 1 to 3 animals (8.8%; P = .004). There was a similar trend for having had an annual checkup (19.3% vs 14.5% [≥ 8 animals] and 16.1% [1 to 3 animals]) and vaccine count (2.38 vs 1.75 [≥ 8 animals] and 2.19 [1 to 3 animals]), but the differences were not statistically significant (P > .05 for all comparisons).

Discussion

More than half of the animals seen in a community-based academic veterinary clinic in Mississippi were from households with more than 1 animal, which is consistent with the rural nature of the sample. Compared with an urban setting, animal owners in a rural area are likely to have increased space, both within the home and on their property, to support multiple animals. Our exploratory aim was to estimate the prevalence of possible animal hoarding in rural Mississippi. Overall, 2.4% of canines and 4.3% of felines lived in a household with 8 or more animals. This is consistent with the prevalence of hoarding disorder, which is typically estimated to be around 2%.²⁰

Although no particular number of animals has been defined in the literature as indicating hoarding, consistent with our hypothesis, the results of the current study indicated that this level of animal ownership is associated with decreased positive indicators of animal care and increased negative indicators of animal health. However, labeling of cases as hoarding needs to be done on an individual basis to determine diagnostic criteria (eg, the household contains more animals than the person in charge of the household can provide adequate care for). Because the most commonly hoarded species are canines and felines, these were the focus of subsequent analyses. However, the total number of animals in each household included noncanines and nonfelines (eg, avian, rodent, reptile, and other small-animal exotics). We also did not differentiate between households with only 1 kind of animal and households with a variety of animal species. Although households with homogeneous animal composition may present differently than households with heterogeneous animal composition, the current investigation was geared toward total animal composition. Although 8 canines may take up more physical space in a house than 8 rabbits or birds, the time and financial burden of caring for the animals still contributes to the overall burden experienced by the owner and thus may lead to increased neglect of the canine or feline in question. Furthermore, because of the cross-sectional nature of the data analysis, we cannot determine causality within the relationship between owning multiple animals and health outcomes. Having ≥ 8 animals in the home may lead to decreased ability of the owner to provide regular health care, or, alternatively, not providing regular health care to animals may decrease a barrier to acquiring more animals (by decreasing the financial burden of ownership). Additional longitudinal research is needed to determine the temporal order of animal acquisition in relation to health outcomes.

To the authors’ knowledge, there are no published data establishing specific health parameters associated with neglect or animal hoarding in private households. Health parameters and environmental conditions are commonly looked at in shelter settings; however, in-depth discussion of animal welfare issues is beyond the scope of this study except for in the context of establishing normative data in this specific study population.

Animal hoarding cases typically take years to get to the point of legal intervention and animal removal.^8,9 Early intervention is key to rehabilitating animals that have been in hoarded houses, both in terms of their physical needs as well as behavioral problems that may have developed.^9,16 Despite the frequency with which individuals who hoard animals cite altruistic intentions,^6,12 animals rescued from hoarded houses tend to have similar outcomes as strays,³ underlining the importance of removing the animals from these detrimental contexts. By quantifying the prevalence of different levels of animal ownership and possible health correlates with having a large number of animals in a household, the present study provided additional background that may later be used to differentiate normal from nonnormative levels of animal ownership, including levels indicative of possible animal hoarding.

Historically, animal hoarding cases have been identified primarily through neighbors and social services.¹ Although veterinarians have the potential to be the first line of detection for animal hoarding cases, further research is needed to determine the best method for early intervention. Collaborative efforts between mental health professionals and community administrators have been successful for object hoarding²¹ and may prove effective for animal hoarding cases as well. One such collaborative effort is already underway in North Carolina and has reported preliminary success in bringing together crisis intervention counselors, law enforcement, and veterinary expertise to identify and treat cases of animal hoarding.¹² In particular, the collaborative approach facilitates more voluntary rehoming of animals and decreases the need for legal action.¹² Interventions designed specifically for animal hoarding have had promising initial results.^7,22 In particular, motivational interviewing has been successfully implemented for equine hoarding, with the intervention being done by field offices.⁷ On an even more basic level, spaying all female cats in a hoarded household was found to significantly reduce the number of cats per household and significantly increase the welfare of the remaining cats.²²

Animal hoarding has been documented across a range of geographic areas, including the US,^1,5,10 Canada,^3,19 Brazil,^4,18 Italy,⁸ Australia,^6,16 and the UK.⁷ However, to our knowledge this was the first examination of normative animal ownership patterns and one of the few studies to analyze a rural sample. We found that at least 2.4% of animal-owning households have probable animal hoarding using a cutoff of > 7 animals/household, and this cutoff was supported by an association with decreased health of the animals seen during veterinary encounters.

Specific limitations of these data were inherent to medical records review, especially in a veterinary medical teaching facility. There is a high turnover of doctors, staff, house officers, and students, creating a distinct lack of continuity in medical record documentation. The physical examination information may be inconsistent or incomplete; however, the records were verified and should therefore be regarded as complete and accurate. Participants self-reported the number of other animals in the household but may have deflated these numbers (eg, to mask animal hoarding) or inflated them (eg, reporting animals not in the immediate household, such as a neighbor’s cats). However, this metric provided the most complete and current measure of the number of animals in a household and closely corresponded to the number of animals seen in the veterinary clinic. Additionally, this study did not account for the presence of other systemic illness that could have contributed to overall poor health despite adequate care by the pet owner. For example, with the location of the current study being rural Mississippi, there may be an overall increased incidence of hydration issues due to a given household being more likely to have a hot dog in it.²³ A veterinary school–based practice is also more likely to provide services for veterinary staff and students, and these individuals may inherently be more inclined to own more animals for a multitude of reasons. These individuals were not excluded, but this study population should be specifically investigated in the future. Finally, an owner may take an animal to multiple veterinarians (eg, due to cost or moving in or out of the area), and thus the number of annual visits, dental visits, and vaccinations may be a lower bound of the true value. Future research is needed to determine whether the health-care indicators used in the current study could be combined with other client-specific parameters to facilitate community efforts to identify and intervene in cases of possible animal hoarding.

Despite the limitations of the current investigation, our results signified the need for increased collaboration between veterinarians and mental health practitioners. We estimated that 2.4% of canines and 4.3% of felines live in a household with ≥ 8 animals, a level that is linked with decreased health care for the animal. Thus, veterinarians working in community settings are likely to encounter such cases and should be equipped with the knowledge and skill to achieve positive health outcomes for both the animals and owners in these situations. We recommend veterinarians reach out to local mental health professionals in their area to determine possible referral networks. In particular, the International Obsessive Compulsive Disorder Foundation provides a resource for finding clinicians specializing in hoarding.²⁴ Finally, we recommend that mental health researchers reach out to local veterinarians to determine the real-world viability of quantitative models.