Ant activity as a source of postmortem bleeding

Case report

The body of a 57-year-old man was found lying on his right side slumped against an ice chest outside a liquor store beside a major city road. Attending ambulance officers noted a considerable amount of blood under the body with linear abrasions suggesting to them that the body had been dragged away from the road. They considered that the most likely scenario was a “hit and run” accident. Police set up a crime scene area and blocked off all lanes of the road. The pathologist who subsequently attended the scene confirmed that the fully clothed body was lying in a pool of blood, but also noted that there were numerous ants crawling over the body and that the “brush abrasions” were more typical of postmortem ant activity (Fig. 1).

Fig. 1

The decedent lying on his right side in a pool of blood that has soaked into his shirt. Cutting of the shirt revealed what were initially considered by attending paramedics to be brush abrasions. Numerous ants can be seen both on and beside the body

At autopsy there was no evidence of acute injury, although there were extensive areas of yellow, parchmented, superficial abrasions with serpigenous margins and adherent ants. These had the typical appearance of postmortem ant predation (Fig. 2). The lesions on the left (upper) side of the body had a typical yellow dried appearance, contrasting with the lesions on the right (lowermost) side, in the areas of dependent lividity, which were congested and hemorrhagic (Fig. 3). The blood at the scene had oozed from these lesions, which were still seeping at the time of autopsy. Other findings at autopsy were of hepatic cirrhosis and old traumatic injury to the frontal and temporal lobes of the brain. Toxicology revealed a blood alcohol level of 0.392 % and a vitreous alcohol level of 0.45 %. No other injuries or underlying medical conditions were present which could have caused or contributed to death, which was therefore attributed to acute alcohol toxicity.

Fig. 2

Typical dry yellow serpiginous lesions resulting from postmortem ant activity removing superficial layers of epidermis. These lesions are on the left side which was uppermost

Fig. 3

Lesions on the dependent right side of the body, however, differed in appearance with a red hemorrhagic appearance with passive oozing of blood

Subsequent information revealed that the decedent had a history of alcoholism, epilepsy and previous traumatic head injuries. He had been drinking at the liquor store the day before death and had been noted by staff to be lying against the ice chest, where he was found in an unchanged position the next morning.

Discussion

Postmortem animal and insect activity tends to be disruptive, sometimes with marked destruction of soft tissue and organs [1]. This is particularly the case when a decomposing body has been infested with fly larvae (maggots). Ants are found on the surface of bodies much earlier in the postmortem period as they feed on keratin derived both from skin and hair, although they may also be found at later stages [2]. The effect of ant pincers is to create parchmented linear lesions with scalloped or serpigenous margins. The lesions are usually yellow–brown in color, as shown in Fig. 2 of the reported case, as loss of the superficial skin layers results in drying. The absence of bleeding has been used to distinguish them from antemortem injuries.

However, a feature that may cause confusion at death scenes, as in the reported case, is the ability of these superficial lesions to cause a considerable amount of blood loss due to injury to superficial capillaries in the papillary dermis [3]. Classically this occurs in dependent areas where engorged capillaries in areas of lividity slowly ooze blood. An additional factor which may have exacerbated the blood loss in the reported case was the presence of significant underlying alcoholic liver disease. Figure 4 demonstrates the effect of the position of the ant excoriations, with the uppermost areas appearing yellow and dry (Fig. 4a), compared to the lower areas on the right side and flank which were congested and oozing blood (Fig. 4b). It has been suggested that formic acid from the ants may also enhance blood loss [4].

Fig. 4

Dried yellow lesions (a) contrasting with hemorrhagic lesions in areas of lividity (b)

It is important at autopsy to determine whether postmortem ant lesions have modified or obscured antemortem injuries. However, this case has clearly demonstrated the effect that body position may have on the appearance of these postmortem injuries, and the potential association of dependent lesions with considerable blood loss after death.