Allan et al. [ 30 ] presented a case study detailing the identification of the biliary protozoal parasite Hammondia heydorni( Figure 2 [ 31 ]) in a raw-fed Alaskan malamute with acute cholangiohepatitis. Although a causal relationship with cholangiohepatitis could not be determined, this rarely reported parasite is becoming of clinical interest, with raw feeding considered a potential contributor to its prevalence.
Raw feeding presents a significant risk in the spread of zoonotic pathogens including Salmonella and E. coli. Bacteria frequently cause food-borne illnesses, with dogs able to transmit bacterial infections to humans even when asymptomatic [ 36 ]. For this reason, the American Veterinary Medical Association [ 37 ] strongly discourages raw diets, to reduce the likelihood of transmission.
van Bree et al. [ 29 ], Mounsey et al. [ 24 ], Groat et al. [ 27 ] and Runesvärd et al. [ 26 ] reported the prevalence of antibiotic-resistant bacteria in raw diets. Mounsey et al. [ 24 ] found E. coli resistant to fluroquinolones, a class of broad-spectrum antibiotics used to treat a variety of infections [ 38 ]. Increasing resistance is likely to affect treatment plans and the health of those infected, including those who acquire antimicrobial-resistant strains from infected dogs fed a raw diet.
Figure 2. A and B: Oocysts of Hammondia heydorni isolated from a dog, seen under a microscope [ 31 ].
Nutritional deficiencies
Despite its significance, few studies have explored nutritional imbalances associated with raw feeding, and the evidence base largely comprises individual cases, often with small populations [ 32 ]. This highlights the need for further research involving larger cohorts.
Hall et al. [ 33 ], similarly to Allan et al. [ 30 ], presented a case study of a 7-month-old bulldog that was fed a raw diet and had severe nutritional deficiencies, including osteopenia and hypocalcaemia secondary to hypovitaminosis D and secondary hyperparathyroidism. While the case underlines the importance of dietary history and owner education, reliance on a single, euthanasia-associated outcome and the potential for publication bias limit the reliability and wider applicability of the conclusions [ 34 ].
A larger-scale study examining nutritional deficiencies in a broader population fed a raw diet is therefore recommended to allow more robust comparisons and conclusions. Hall et al. [ 33 ] portray a markedly negative outcome, but not all cases conclude negatively, reinforcing the need for further research to fully understand nutritional deficiencies associated with raw diets.
Discussion
With raw feeding increasing in popularity, veterinary practices should be prepared to diagnose and treat nutrition-related conditions [ 35 ]. As VNs play an important role in owner education and support, understanding the negative complications of a raw diet is vital to ensure the risks are minimised [ 8 ].
Additionally, Mounsey et al. [ 24 ] concluded that feeding meat marketed as pet food is equally as likely to transmit antibiotic-resistant bacteria. van Bree et al. [ 29 ] provided evidence of this, finding E. coli in 86 % of raw diets analysed, alongside Salmonella. In practice, isolation and barrier nursing should be encouraged and feeding raw diets discouraged to minimise the spread of zoonotic disease [ 39 ]. However, isolation is not always possible in smaller practices, so barrier nursing is vital.
Martinez-Anton et al. [ 25 ] found raw chicken consumption to be a risk factor in the development of APN, potentially in the context of Campylobacter infection. Additionally, because it contains smaller bones, raw chicken is more likely to be incorporated into the diets of smaller breeds, thus increasing the association. Groat et al. [ 27 ] found that 86 % of participants incorporated raw chicken into their dogs ' raw diets. With raw chicken proving popular, practices may see an increase in Campylobacter infections and related conditions, due to the significant role of raw poultry in its transmission [ 39 ].
Groat et al. [ 27 ] found that improved stool consistency, oral hygiene and behaviour were factors contributing to an owner ' s choice to feed their dog a raw diet. However, in feeding a raw diet, owners often disregard their own safety and can increase the risk of zoonotic transmission [ 40 ]. VNs must encourage and highlight the importance of appropriate handling, storage and sourcing of raw pet food to minimise zoonotic transmission, which may prove detrimental to human and canine health.
Parasites are an increasingly prevalent issue in relation to raw diets, meaning it is vital that VNs are knowledgeable about parasitic species. This knowledge should be shared with owners to minimise the risks of parasitic infection [ 41 ]. van Bree et al. [ 29 ] identified Sarcocystis alongside T. gondii in 29 % of examined raw diets. Livestock serve as intermediate hosts of Sarcocystis. The inability to test the meat ingredients of raw diets throughout
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