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Poisonous animals
Cnidarians (Jellyfish, Corals and Anemones)
Venomous fish
Hymenopterans (Bees, Wasps and Ants)
Sea snakes
Terrestrial snakes
Miscellaneous animals



Latrodectus spp.




Latrodectus sp.

Clark et al. 1992: 163 Latrodectus sp. bites (retrospective chart review). Inclusion criteria: either a positive black widow spider identification or a visible envenomation site ("target lesion"). Depending on the clinical presentation, patients were categorized as grade 1, 2, or 3 in severity.


South Africa
Latrodectus indistinctus / Latrodectus geometricus

Müller 1993: 45 spider bites. Identification: L. indistinctus brought in and identified 6/30; indirect: typical signs and symptoms of Latrodectus envenoming that were severe enough to indicate administration of antivenom, plus improvement of the symptoms 6–12 h after antivenom administration. L. geometricus brought in and identified 10/15; satisfactory description by the patient 5/15.

Latrodectus hasselti

Sutherland and Trinca 1978: 2,144 spider bites. Method: questionnaire that was included with antivenom vials and sent in by treating doctors. Identification: attributed to L. hasselti; 20% of the cases were insufficiently documented. Over 95% of patients received antivenom. This was observed to alter the course of envenoming.

Wiener 1961: 167 spider bites. Method: questionnaire given to doctors. Identification: attributed to L. hasselti.

Isbister and Gray 2002: 56 Latrodectus hasselti bites (prospective cohort study of 750 definite spider bites with expert spider identification: 44/750 significant effects, including 37/56 Latrodectus hasselti bites). Identification: Spider collected and expertly identified.

Isbister and Gray 2003: 68 Latrodectus hasselti bites (prospective cohort study). Identification: Spider immediately collected and expertly identified.

Case reports

South Africa
Latrodectus indistinctus
La Grange 1990: 1 case. Identification: spider brought in, L. indistinctus.
Rayner 1987: 1 case. Identification: spider brought in, L. indistinctus.
Visser and Khusi 1989: 1 case. Identification: L. indistinctus recognised from a photo.

Signs & symptoms

Autopharmacological effects

Experimental and clinical observations suggest that the major systemic effects of envenoming are caused by endogenous catecholamines and acetylcholine, which are released in response to Latrodectus venom. As these are transmitters of the sympathetic, parasympathetic and somatic nervous systems, the resulting clinical symptoms of envenoming are dealt with in the section "Neurological effects".

Local effects

Local burning pain during the bite (may be absent and thus the bite may go unobserved). The pain may spread in the direction of the regional lymph nodes within minutes (5–15 min). Local erythema, oedema, hypaesthesia (Maretic 1978a, 1983, Rauber 1983–84). So-called "target lesions" (circle of reddened skin surrounding a pale centre) with a diameter of 2–6 cm can develop within 1–2 h and disappear again after 8–12(–24) h (Vance et al. 1986).

Latrodectus indistinctus
Burning pain at the site of the bite (20/30), painful regional lymph nodes (7/30), obvious puncture wound (20/30) (Müller 1993).

Latrodectus geometricus

Burning pain at the site of the bite (14/15), painful regional lymph nodes (3/15), obvious puncture wound (12/15) (Müller 1993).

Latrodectus hasselti
Pain (not further defined) 150/167 (Wiener 1961); local pain 1,629/2,144 (Sutherland and Trinca 1978); erythema 33/167 (Wiener 1961), 708/2,144 (Sutherland and Trinca 1978); oedema 30/167 (Wiener 1961), 51/2,144 (Sutherland and Trinca 1978); pain or swelling of the regional lymph nodes 7/167 (Wiener 1961), 407/2,144 (Sutherland and Trinca 1978).

Pain 68/68, severe in 42/68, pain lasting > 24h 45/68, unable to sleep because of pain 22/68 (Isbister and Gray 2003).

Neurological effects (autonomic and somatic nervous systems)

Latrodectus envenoming is characterised by generalised autonomic and neuromuscular effects. Latrodectus venom causes a massive release of the two neurotransmitters noradrenaline and acetylcholine. Both parts of the autonomic nervous system and the somatic nervous system are stimulated. This results in cholinergic effects (vomiting, profuse sweating, hypersalivation, priapism, bradycardia) and adrenergic effects (arterial hypertension, tachycardia, cardiac arrhythmias). Stimulation of the somatic nervous system has the following effects on the skeletal musculature: muscle fasciculations and spasms, generalised muscle pain and cramps, particularly in the regions of the abdomen, chest, back and thighs, within 1 h after the bite. The pain in the larger muscle groups increases rapidly until it becomes unbearable. Strong, cramping abdominal pain and board-like abdominal rigidity have been misdiagnosed as acute abdomen, leading to unnecessary laparotomies. Feeling of weakness and difficulty in walking.

In rare cases pulmonary oedema was observed (aetiology: cardiogenic/non-cardiogenic?). State of anxiety.

If untreated, these symptoms may persist for days (Maretic 1978a, 1983, Rauber 1983–84).

Latrodectus indistinctus
Symptoms: generalised muscle pain and cramps 24/30, abdominal pain and cramps 20/30, painful extremities, in particular the legs 17/30, cramping pain of the back muscles 14/30, weakness of the legs, difficulty in walking 14/30, chest muscle cramps 9/30, headache 6/30, nausea, vomiting 5/30, paraesthesias of the hands and feet 4/30.
Signs: sweating 21/30, rigidity of the abdominal muscles 21/30, arterial hypertension, tachycardia 18/30, restlessness, agitation 15/30, very active deep tendon reflexes 9/30, increased muscle tone 6/30, reduced grip and pinch strength 5/30, raised temperature 5/30, muscle fasciculations and tremor 4/30.
For 22/30 patients it was known at what time the bite occurred. The time between the bite and the onset of systemic signs of envenoming was 15–60 min (Müller 1993).
Pulmonary oedema (La Grange 1990, Visser and Khusi 1989).

Latrodectus geometricus
Symptoms: generalised muscle pain and cramps 2/15, abdominal pain and cramps 4/15, painful extremities, in particular the legs 1/15, cramping pain of the back muscles 1/15, weakness of the legs, difficulty in walking 2/15.
Signs: sweating 1/15, rigidity of the abdominal muscles 1/15, restlessness, agitation 2/15, raised temperature 2/15. Latrodectus geometricus causes milder envenoming than Latrodectus indistinctus; chiefly local signs and symptoms (Müller 1993).


Latrodectus hasselti
Generalised pain (plus local) 150/167 (Wiener 1961); generalised pain 836/2,144 (Sutherland and Trinca 1978); nausea/vomiting 40/167 (Wiener 1961), 429/2,144 (Sutherland and Trinca 1978); sweating 63/167 (Wiener 1961), 322/2,144 (Sutherland and Trinca 1978); paraesthesias 12/167 (Wiener 1961), 214/2,144 (Sutherland and Trinca 1978); fever 13/167 (Wiener 1961), 172/2,144 (Sutherland and Trinca 1978); insomnia 17/167 (Wiener 1961), 172/2,144 (Sutherland and Trinca 1978); muscle weakness 18/167 (Wiener 1961); muscle spasms/tremor/rigidity 40/167 (Wiener 1961); arterial hypertension 3/167 (Wiener 1961), 64/2,144 (Sutherland and Trinca 1978).

Systemic effects 24/68 (nausea, vomiting, headache, lethargy, generalized diaphoresis) (Isbister and Gray 2003).

Other signs & symptoms

Latrodectus indistinctus

Reddened, swollen face, particularly around the mouth, conjunctivitis (Maretic 1978a, 1983, Rauber 1983–84).

Swelling of the face, particularly the eyelids 10/30 (Müller 1993).


Case fatality rate

Older reports cite mortality rates of up to 6% (Bogen 1932). However, more recently no fatalities have been reported.

0/45 (Müller 1993).
0/177 (Maretic 1983).


Laboratory and physical investigations

1. CPK
Increased: 1,901 U/l (Müller 1993).

2. Leucocytes
Leucocytosis: 11,000–18,000/mm³ (6/10) (Müller 1993).

Treatment (symptomatic)

1. Monitoring of patients

All patients with systemic envenoming should be hospitalised and, if necessary, monitored in an intensive care unit.

2. Patients with respiratory failure
Endotracheal intubation and artificial respiration.

3. Fluid replacement

Optimal hydration via fluid replacement (if necessary i.v.) in order to avoid prerenal renal failure (Müller 1993). Sweating and vomiting can cause marked fluid loss. Estimated fluid loss in a patient over 48 h due to profuse sweating 8 litres (Rayner 1987).

4. Calcium gluconate

Calcium gluconate 10–20 ml i.v. for 15–30 min is the only drug that is effective in relieving muscle pain and cramps. However, its duration of action is only 20–30 min and the number of repeat doses that can be given is limited due to adverse reactions (Müller 1993).


5. Contra-indicated medications and medications to avoid

Opiates and other centrally sedating medications, such as benzodiazepine, are not only largely ineffective, but also dangerous. They can lead to respiratory depression in patients with pre-existing damage (Müller 1993).

Treatment (specific)


1. Spider antivenom (SAIMR, Johannesburg, South Africa)
Müller 1993: (study design, see above).

Dose: 1 vial of 5 ml i.m. (29/30); within 12 h after the bite 20/30, between 12 and 24 h after the bite 3/30, after 3–5 days 3/30, no time given 3/30; 2 vials administered 2/30 (Müller 1993).

Efficacy: All patients improved within 6–12 h after antivenom administration. In 19/30 the symptoms of envenoming disappeared completely within 6 h, in 7 the effect was dramatic, with clear improvement within 30–60 min. 4 patients were symptomatic until they were given antivenom between 3 and 5 days after the bite (Latrodectus indistinctus 3/4, Latrodectus geometricus 1/4).

Adverse reactions: No allergic reactions 29/29.


La Grange 1990: one patient still had the classic signs of Latrodectus envenoming 36 h after the bite, as well as pulmonary oedema. She received antivenom 48 h after the bite. She started to improve within 2 h.


2. Red-back spider antivenom (CSL, Parkville, Australia)
Sutherland 1992: 256 cases in which Red-back spider antivenom was used and which are sufficiently well documented.

Dose: 1 vial 217/256, 2 vials 33/256, 3 vials 5/256, 4 vials 1/256.
Efficacy: Good results, even when antivenom was administered up to 120 h after the bite.
Adverse reactions: Immediate hypersensitivity 2/256, delayed reactions (serum sickness)  3/256.


Isbister and Gray 2003: 68 Latrodectus hasselti bites. Identification: Spider immediately collected and expertly identified. Hospitalized patients: 23/68 with antivenom treatment  (i.m.) in 6/23. No significant difference in pain relif and duration of systemic effects between the treated and non-treated group.


Conclusions and recommendations

Antivenom is the only effective treatment for severe envenoming caused by Latrodectus sp. (Maretic 1983, Müller 1993, Sutherland 1983). Thus antivenom is recommended for all patients with severe systemic envenoming.

Antivenom should be administered in most cases for pain relief alone, but the intramuscular route needs to be reconsidered with a controlled clinical trial (Isbister and Gray 2003).

Although calcium gluconate usually has been considered the first-line treatment of severe envenomations by black widow spiders, it was found ineffective for pain relief compared with a combination of i.v. opioids and benzodiazepines. The use of antivenin significantly shortened the duration of symptoms in severe envenomations (Clark. et al 1992). Overall, the use of calcium gluconate to relief painful muscle spasms is not based on sufficient evidence.