Tissue necrosis after canine bothropic envenoming: a case report

Case report

TISSUE NECROSIS AFTER CANINE BOTHROPIC ENVENOMING: A CASE REPORT

R. S. FERREIRA JÚNIOR1; B. BARRAVIERA^1,2

1 Center for the Study of Venoms and Venomous Animals - CEVAP, São Paulo State University - UNESP, Botucatu, São Paulo, Brazil; 2 Full professor of the Department of Tropical Medicine and Imaging Diagnosis, Botucatu School of Medicine - FMB, São Paulo State University - UNESP, Botucatu, São Paulo, Brazil.

ABSTRACT: The authors report a case of bothropic envenoming in a male Cocker Spaniel. The animal was bitten in the ventral thoracic region, receiving treatment 4 hours later. Clinical examination revealed an extensive, painful and area of firm edema, absence of local or systemic hemorrhage, without evident neurological alterations. Clinical diagnosis was mild bothropic envenoming. Treatment consisted of 5 vials of polyvalent snake antivenom, two vials administered intravenously and three subcutaneously. Blood clotting time was always within normal values. Two days after envenoming, the animal showed hyperthermia and received enrofloxacin (5mg/kg/24h) for 10 days and ketoprofen (1mg/kg/24h) for 5 days. Seventy-two hours after envenoming, extensive subcutaneous, muscle fiber, and skin necrosis of approximately 10 cm in diameter was observed. After débridement of necrotic tissues, the area was cleaned with antiseptic solutions. Complete healing was observed 55 days after envenoming. The authors discuss whether heterologous serotherapy is effective in preventing tissue necrosis after bothropic envenoming.

KEY WORDS:Bothrops, necrosis, bothropic envenoming, dog.

INTRODUCTION

The most common snakes involved in envenomings in Botucatu region- São Paulo - Brazil, are from genus Bothrops and Crotalus (1). Veterinarians should be able to identify the type of envenoming by both clinical characteristics and snake identification.

The most evident symptom of bothropic envenoming is progressive edema and necrosis at the bite site. Hemorrhage can also occur.

For appropriate animal care, the location of the bite and the species of bitten animal need to be considered.

In Brazil, there are specific antivenoms and polyvalent ones, which neutralizes both bothropic and crotalic venoms, but the most easily available for veterinarians is the polyvalent one.

In bothropic envenomings, despite the appropriate treatment, many animals show complications similar to this case report.

CASE REPORT

A male black Cocker Spaniel, aged 4 years and weighing approximately 12 kg. According to the owner, the animal was playing by the side of a river when it began howling and barking, and a painful edema was seen in the ventral thoracic region. The animal was treated 4 hours after the bite. The owner did not give the animal any medication.

Clinical examination showed dyspnea with firm edema in the ventral thoracic region with rectal temperature 39.5°C, capillary perfusion time (CPT) 1'', hyperemic mucous membranes, pain, and increased of local temperature. Hemorrhage was not observed. Fang marks could not be seen, only erithematous skin scratching. Blood clotting time was 5'30'', which was normal

The symptoms and clinical signs led us to the diagnosis of mild bothropic envenoming. The animal received 5 vials of polyvalent antivenom Vencofarma®. Two vials (20 ml) were injected IV and three vials (30 ml) by SC route. Hydration was performed by administering 300 ml of Ringer's lactated.

The animal was observed for 4 hours, without showing any signs of anaphylactic reaction. When breathing returned to normal, the animal was discharged. No medication was prescribed, only hot and wet compresses to reduce edema.

Two days after envenoming, the animal was apathetic with rectal temperature 40°C, clotting time 6', pale mucous membrane, and CPT 3". The local edema was large, spreading towards the ventral abdominal region and prepuce. Palpation showed intense local pain with hot edema of firm consistency. Local necrosis was not observed. Hydration was performed by IV administration of 200 ml of Ringer's solution. Enrofloxacin 5 mg/kg every 24 hours and ketoprofen 1 mg/kg every 24 hours were prescribed.

On the fourth day (Figure 1), the animal returned to the hospital with 2 big necrosis areas of 10 cm in diameter each: one at the bite area and the other in the abdominal region cranially to the penis. Examination showed that the animal was alert showing normal parameters with temperature of 39°C, hydrated, and mucous membrane of normal color. The wounds were cleaned using povidine diluted in saline. Débridement of wound edges was performed and furazolidine (Furacin®) was applied. Cleaning with Dakin's solution, compresses with potassium permanganate for 5 min, and furazolidine (Furacin®) and sugar three times a day were prescribed.

On the 11^th day (Figure 2), clinical examination showed that the animal's condition was good, with temperature 39.2°C. The wounds showed granulation tissue. The wounds and their edges were cleaned using povidine diluted in saline, and furazolidine (Furacin®) was applied. Cleaning using Dakin's solution, potassium permanganate compresses for 5', and furazolidine (Furacin®) and sugar twice a day were prescribed.

On the 17^th day (Figure 3), the animal was alert with temperature 38.8°C. The wounds showed granulation tissue, with about 50% regression. The wound and its edges were cleaned with povidine diluted in saline, and furazolidine (Furacin®) was applied. Cleaning with Dakin's solution, potassium permanganate compresses for 5', and Furacin® and sugar twice a day were prescribed.

On the 25^th day (Figure 4), the animal's condition was good, with temperature 38.5°C, mucous membrane of normal color, CPT 2", and clean non-purulent ulceration with well-defined borders and 80% reduction. The wounds and their edges were cleaned with povidine diluted in saline and furazolidine (Furacin®) was applied. Cleaning with Dakin's solution, potassium permanganate compresses for 5', and Furacin® and sugar once a day were prescribed.

On the 55^th day (Figure 5), the wound was completely healed.

DISCUSSION

Bothropic envenomings in the Botucatu region, São Paulo state, Brazil, are generally caused by Bothrops neuwiedi, B. jararaca, and B. alternatus. These constitute about 80% of all snake envenomings (1). In this study, the animal's evolution and clinical picture allowed us to suggest that this was a bothropic envenoming (1,2).

Statistics about snake envenomings involving domestic animals are scarce in veterinary literature, which justifies this case report. Despite early treatment, evolution was not favorable. The edema was relevant, leading to subcutaneous, muscle fiber, and skin necrosis.

Bothrops venom produces rapidly spreading edema and necrosis, which have for long been attributed to their proteolytic activity (5,8). However, it is not yet known whether these local venom effects can be reproduced by purified components, such as hemorrhagic principles or proteases, nor whether the proteolytic activity of the components run parallel to their tissue damaging action (3,5).

Muscle necrosis is a relevant local effect induced by many snake venoms, as it may lead to permanent tissue loss, disability, and amputation (7). Clinical studies have described a generally limited effectiveness of antivenom serotherapy in preventing the development of local tissue damage (8). Necrosis of the muscle fibers occurs only after hemorrhage. Myonecrosis may be attributable to primary venom action or is secondary to a collapse of the microcirculation (6).

Almost all snake toxins with a direct muscle damaging activity isolated to date are basic proteins (7). At present, three metalloproteins have been isolated from Bothrops jararaca venom (5). Two of these are hemorrhagic factors: HF1, which has no detectable proteolytic activity on casein; and HF2, which has very low proteolytic action. The other component, bothropasin, is a metalloprotease with no detectable hemorrhagic activity (5).

Results show that local effects of Bothrops venom, such as hemorrhage, myonecrosis, and arterialnecrosis can be completely reproduced by its purified hemorrhagic factor at doses 20 times smaller (4).

The greater tissue damaging potency of HF2 suggests that in Bothrops jararaca envenomation, hemorrhagic factors may play a major role than the proteases (5).

In general, antivenom ability to prevent local tissue damage, even when administered immediately after experimental envenomation, has been only partial (8).

In this study, the animal was bitten in a region of low muscular mass, not head or limbs; when the animal was treated, its clinical signs indicated mild envenoming. Five vials of antivenom were given so that the animal's physiological condition could return to normal. Due to the size of the edema, the envenoming should have been classified as moderate, and 5 additional vials were injected IV to reduce necrosis.

In conclusion, these results are in agreement with the generally accepted view that local tissue damage induced by snake venoms is difficult to prevent by serotherapy (8).

Received 04 October 2000

Accepted 01 March 2001

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Publication Dates

• Publication in this collection
  08 Oct 2002
• Date of issue
  Dec 2001

History

• Received
  04 Oct 2000
• Accepted
  01 Mar 2001