Chronicle Editor
THE heavens have been generous, giving us so much rains.
The young and the young at heart have been busy in the fields making the most of the farming season.
The elderly patients on chronic treatment, that usually come in monthly for consultation, have requested a few months’ supply of medication that will see them through the rainy season in their rural homes.
The precipitation fills the underground habitats of various flora.
This brings its own hazards as the creatures of the wild seek refuge in our cosy homes.
Spiders, scorpions and snakes are on the prowl in the woodpiles, dark corners, cupboards, under beds and in the blankets.
This week we shall have a closer look at spider bites and how to manage them.
Many of Zimbabwe’s spider species are harmless, there are a few particularly large and/or venomous species.
Like most animals, spiders are inherently afraid of humans and usually go out of their way to avoid them. Spiders play an important role in the ecosystem.
They eat many insects that pester or even harm humans, including mosquitoes that can transmit deadly diseases and agricultural pests — including aphids, grasshoppers, leafhoppers, beetles, and caterpillar — that feed on the fruits, leaves, stems, and seeds of crops that we harvest for food.
(Science Friday — the ecological importance of spiders).
Common symptoms and signs from spider bites that can be experienced can be local or systemic (affecting the whole body).
Local signs pain, redness, swelling, itching, numbness, blistering and induration from bite marks (two fangs).
Systemic symptoms from bites include fever, sweating, nausea and vomiting, shortness of breath, abdominal cramps, hypertension, joint pain and weakness, perspiration, urinary retention, swelling of eyes and muscle twitching.
Rare complications include myocarditis (heart muscle effects), rhabdomyolysis (destruction or degeneration of muscle tissue), paralysis and renal failure and coma.
Bites can be cytotoxic, (toxic to cells, cell-killing), hemotoxic (destructive to red blood cells) or neurotoxic toxins (that are destructive to nerve tissue).
(Mednet-biodefinations).
Rain spiders are named for their habit of entering houses just before the summer rains. Its usual habitat includes woodpiles, spaces between walls, disused storages area.
Bite site may become dark or red-like within 24 to 72 hours.
They are cytotoxic and hemotoxic.
The rain spider’s venom is weak, so that symptoms are no worse than a common bee sting. Bites usually heal by themselves in a matter of days.
Sac spiders are thought to be responsible for most spider bites in Zimbabwe.
Their venom is cytotoxic, which means that it kills cells and causes tissue breakdown and blistering at the bite site. Bites are considered painful and potentially scarring, but not life threatening. They are found in kitchens, bathrooms and other rooms with plumbing. They attack when cornered, squashed or provoked, causing moderate to intense pain on bite site but tend to recover rapidly. In 2011 the yellow sac spider caused a recall of the Mazda 6 automobile, because the spiders could not resist the smell of petrol emitted by the unusual dual pipes coming from the vehicles’ gas tanks and built potentially hazardous webs inside the cars’ emission system. (Medscape).
Baboon spider are a sub-family of tarantula, they are large, hairy, and capable of inflicting a painful bite.
Baboon tarantulas are venomous; however, they are unlikely to attack unless provoked.
They live in burrows which they line with silk and use to ambush insects and small reptiles, though some live in trees. Female baboon spiders can live for as long as 30 years.
The black widow/button spider is a very venomous species.
The venom of these spiders is highly neurotoxic, and females have the potential to kill a child or an infirm adult.
They typically stay away from human residences and are most often encountered in rural areas.
Brown button spider species is approximately four times less toxic than that of a black button spider.
They are often found in garages and packing crates, generator housings and pump boxes. Reaction to envenomation is typically minor.
Violin spider, their venom destroys tissue, causing a specific kind of skin necrosis (tissue destruction).
The danger of secondary infection is high if left untreated.
Fortunately, violin spiders are shy by nature, and rarely bite humans.
They are nocturnal and nest under rocks and logs rather than weaving webs.
The six-eyed sand spider a name that translates as ”murderer” in Latin. Indeed, this species’ bite has been proven capable of killing a rabbit in under 12 hours.
Its venom is both hemotoxic and cytotoxic, causing leaking blood vessels and destroyed tissues.
Most bites are on assumption by the patient or the doctor.
Positive identification proves to be a challenge for both doctor and patient.
Treatment is mainly supportive and includes:
λ Clean the wound. Use mild soap and water and apply an antibiotic ointment.
λ Apply a cool compress. Use a cloth dampened with cold water or filled with ice. This helps reduce pain and swelling.
λ If the bite is on an arm or leg, elevate it.
λ Take an over-the-counter pain medication if needed.
λ If the wound is itchy, an antihistamine.
λ Loose immobilisation and local debridement of the affected area.
λ Antivenom is not widely produced.
Till next week stay safe and try maintaining clear surroundings in and around the homestead.
ν Dr Tatenda Simango can be contacted on [email protected] or follow him on Facebook@9th Avenue Surgery. Book an appointment on www.9thavenuesurgery.co.zw
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