Introduction

Diabetes mellitus, being a multisystemic disease presents with peripheral neuropathy in a large population of patients, predisposing to foot ulcers.^1-7

Rat bite is an uncommon cause of foot ulcer in persons living with diabetes. It can be fatal and may be associated with rat bite fever, tetanus and rabies.^8-11

Artherosclerosis and peripheral neuropathy are underlying mechanisms associated with the occurrence of diabetic foot ulcers.¹² People with diabetes mellitus have a higher incidence of atherosclerosis, thickening of capillary basement membrane, arterial hyalinosis and endothelial proliferation.¹²

Other factors that increase the likelihood of peripheral artery disease include smoking, hypertension, high blood cholesterol levels, being overweight, sedentary lifestyle, previous or existing history of heart disease.

The pathophysiology of diabetic foot ulcers has neuropathic, vascular and immune system components, which all show a base relationship with the hyperglycemic state of diabetes^.13-14

Hyperglycemia produces oxidative stress on nerve cells and leads to neuropathy.¹³

Patients do not notice foot wounds because of decreased peripheral sensation like in our patient.

Peripheral neuropathy combined with poor arterial flow confers a high risk of limb loss on patients living with diabetes.

A history of traumatic, painless, non-smelling ulcers in a setting of severe neuropathy, poor glycemic control and rural residence may lead one to suspect rat bite as a cause of diabetic ulcers. Here, we report a case of foot ulcer caused by rat bite on background of diabetes mellitus and peripheral neuropathy.

Case Report

A 65 year old male pastor who presented on account of right foot ulcer of 3 weeks duration. He had type 2 diabetes mellitus for the past 15 years with bilateral peripheral neuropathy as a complication. He takes Metformin 500 mg daily and was said to be compliant with his medications. On the day of presentation, he noticed rat bite marks on his right fifth toe, which he noted not after the bite but when the site started bleeding. The ulcer was been dressed regularly at a peripheral hospital but did not show much improvement. There was no history of fever but there was positive history of numbness of legs and tingling sensation on the upper limbs. He was not a known hypertensive (Table 1).

His random blood glucose on admission was 417 mg/dl. He claimed that insulin makes him more forgetful than usual so has not been on insulin since he was diagnosed of diabetes.

His clinical examination revealed stable vital parameters, gangrenous 5th toe of the right foot with surrounding hyperpigmented skin, and absent dorsalis pedis bilaterally. Neurological examination showed that light touch and joint sense were intact.

Investigations requested showed mild anaemia, neutrophilic leucocytosis, proteinuria and dyslipidaemia. Glycated haemoglobin was deranged, 8.7% and wound swab culture isolated significant growth of mixed organisms, Staph aureus and Klebsiella.

He was treated with insulin, metformin, ceftriaxone, tinidazole, dabigatran, vitamin supplements and rosuvastatin.

He was also given intramuscular tetanus toxoid and the wound was dressed daily with normal saline and povidone iodine. The orthopaedic team was invited to review and they counselled patient on the relevance of an ablative surgery which he refused. Patient continued to make noteworthy recovery but was yet to carry out requested investigations due to some financial constraint (Table 2).

Discussion

Rat bites primarily affect children aged 5 years and below who lack the ability to respond to the pain sensation caused by the bite.⁶ however, adults are not immune to rate bites.

The prevalence of neuropathy increases with increased duration of sub-optimal glycemic control. Patients living with diabetes that have peripheral neuropathy are more prone to risk of rat bites especially in environment with poor sanitation and large rat population. Rat bites in subjects with diabetes present with significant morbidity with progressing infection, limb amputation and even mortality (Table 3).^15-17

In a series from India, the patients were all from rural backgrounds with prolonged diabetes and the most common site of bite being in the extremities, the presentation being similar to the patient in this case report who lived in a rural setting (Ahiazu Mbaise, Imo State). There was also a case report of diabetes foot ulcer following a rat bite published in December 2013 by the department of medicine, Federal Medical Centre, Umuahia Abia State sharing some predisposing factors to the rat bite in our patient which includes: rural setting, peripheral neuropathy and poor glycemic control.

In Nigeria, cases of rat bites and diabetic foot are scarcely reported, may be due to the facts that it occurs during their sleep and patient may not realize that they were bitten.

In this index patient, the bite marks were very distinct. Most of these patients present late to the hospitals because of the ideology that these marks might have been spiritual attacks, so they tend to spend more time seeking spiritual help than medical help especially within rural areas.

This was not the case in our index patient because the marks were distinct to rat bite marks even though that may not be enough to convince all patients with the same issue that this is not a spiritual issue.

Conclusion

Diabetic patients need to keep their houses and environments free of rodents, and they should cover their feet while sleeping, for example wearing loose fitting socks.

Rat bite preventive strategies should be included in diabetic foot care education in areas such as ours.

Acknowledgment

None

Conflicts of Interest

The author declares that there are no conflicts of interest.

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