Revenge of the Killer Snails

CONE SHELL MOLLUSC POISONING, WITH REPORT OF A FATAL CASE

 
Reports of instances of fatal poisoning by the various species of cone shell, Conus, are so rare that it seems that no such case occurring in Australian waters has until this year (1936) been recorded. Professor J.B. Cleland has collected the literature and described in considerable detail in The Australasian Medical Gazette of September 14 and 21, 1912, the cases of poisoning by different species of Conus recorded up to that time. These may be summarized as follows: 

Non-Fatal Cases

I. A. Adams ("Zoology of the Voyage of Her Majesty's ship Samarang", 1850, page 19). Sir Edward Belcher was bitten as he picked up the Conus aulicus from the water at Mayo, one of the Moluccas. The wound received was accompanied by acute pain, and consisted of a small, deep, triangular mark succeeded by a watery vesicle. The pain was compared with the burning of phosphorus beneath the skin. According to J.E. Gray (Annals of Natural History, Volume XII, April, 1853, page 178), in this instance the cone hung on like a leech. 

II. Crosse and Marie (Journal de Conchologie, Volume XXII, 1874, page 353). A Ponebo native, New Caledonia, was stung on the hand by Conus textile. The hand and arm were considerably swollen and severe pain persisted for some time. 

III. A. Garrett (Journal of Conchology, 1878, page 365). When collecting at Panmotus, the writer was bitten by one of three specimens of Conus tulipa which he held in his hand while searching for others, when the long, slender proboscis punctured a finger, causing sharp pain not unlike the sting of a wasp. 

IV. B. Hinde (Proceedings of the Linnean Society of New South Wales, Volume LX, 1885, page 944). The author saw a native on the island of Matupi., New Britain, who had been bitten by a Conus geographus and who had at once cut small incisions with a sharp stone all over his arm and shoulder. The blood flowed freely and the native explained that, had he not done so, he would have died. 

V. Dr. A. H. Hallen reports that a native in Fiji, who had cracked the shell of a Conus geographus, handed it to his European mistress. To extract the soft parts from the shell, she inserted the little finger, when she felt the animal shoot out a sharp pointed thing which made her call out at once that she was bitten and poisoned. The point of the puncture was minute and only to be seen with great care. Locally it caused a bluish discolouration near the side of the nail. The effects were most grave. First a local numbness spread rapidly up the arm which became paralysed. The paralysis spread rapidly throughout the body. Not only was general muscular control abolished so that even the head had to be supported to permit breathing, but there was loss also in a lesser degree, it is thought, of sensation, with numbness and "pins and needles" beginning in the arm and becoming generalized, with disappearance of muscular sense and complete absence of knee jerks. Utterance was thick and indistinct. The cardiac and respiratory apparatus did not participate to a dangerous degree in the paralysis. When at its worst, three or four hours after the patient was bitten, the condition distinctly affected the throat and distress was caused by the difficulty in removing accumulated fluid. Micturition was involuntary. The worst was past in about six hours, but the paralysis persisted with diminishing intensity until next day. Numbness lasted considerably longer in the injured finger, and for a month afterwards she experienced a shock in the little finger on hard impaction, as when playing the piano. 


The above five cases were all non-fatal. There does not appear to be any first hand description in any medical publication, even when the patients were seen by medical officers, the instances quoted being mostly from non-medical journals. Numerous hearsay and otherwise non-recorded instances, generally in natives, are mentioned without any great detail. 


A relatively recent account of a non-fatal "Conus geographus envenomation", was given by David Fegan and David Andresen in the medical/scientific journal, The Lancet 349: page 1672, (1997). This case was treated at Honiara Central Hospital, Solomon Islands. "A 24-year-old male nurse was admitted with a 12-h history of progressive generalised weakness and poor coordination. The previous night, while collecting seashells, he had suddenly felt a mild stinging sensation in his right hand. His systemic symptoms began about 30 mins after this local injury. On examination he had a small puncture wound on the middle finger of his right hand., without erythema or swelling. He was dysarthric, had bilateral ptosis, and an absent gag reflex. All peripheral muscle groups were weak, and his coordination was impaired without cerebellar features. His peak expiratory flow rate was 290 L/min (predicted 600 L/min). The remainder of his physical examination was normal. The shell responsible for the injury was recovered by his relatives. He was admitted for observation and a portable pulse oximeter was used to monitor the adequacy of his ventilation. His oxygen saturation remained above 95% on room air. 12 h after admission he developed acute urinary retention for which he required catheterisation. Although weak, he could walk unaided after 48 h. He was discharged after 72 h at which time his physical examination was normal. When reviewed at medical outpatients a month later he had no complaints." 

Non-fatal stings in Hawaii
In 1959 Roland M. Gray of San Diego, wrote an article about his diving experiences (in the period 1956 to 1958) in Hawaii entitled "Reminiscences of Diving and Related Activities in Hawaii, Part 4" [reprinted in the HMS Bulletin, July 1999, pp. 3-8] in which he relates the story of "a fellow shell collector, C.L. Wikerson, PR2, USN, who worked in my shop and dove with us several times was stung by a small Conus textile that was reported to be about 1.5 inches in length. His experience, as related to our group and later published in the August 1, 1956 issue of the Hawaiian Malacological Society Shell News, deserves recounting and is quoted verbatim below:" 

"He was diving of Nanakuli seeking shells in the sand bottom. Noticing a shell half buried in the sand he picked it up, when almost immediately the cone stung him on his middle finger. Despite sucking the wound to draw out any poison, within fifteen minutes he developed a bad headach. During the next twelve hours at home he was extremely nauseated, followed by painful stomach cramps through the night. He stated that shortly after the initial sting he experienced a noticeable shortness of breath, almost, as he described it, as if someone was sitting on his chest. By the next morning these symptoms had ceased but the wounded finger continued to pain him".

 "Considering that this particular Conus textile was a very small member of its species, the potency and peril represented by a larger specimen can easily be envisaged".

 "The only other Conus sting incident I was aware of during my stay in Hawaii involved a shell collector who was not a member of our immediate group. He stated that he had just returned to the beach after collecting several shells, among them a Conus halitropus, now known as Conus obscurus. The shell is oval in outline and very light in weight. The outer lip is very thin, flaring, and encloses a wide aperture. The color is a yellowish-brown that is marked by irregular flesh colored areas. It reaches a maximum length of about 1 3/4 inches. For lack of a better place to put the cone he placed it on his head beneath a navy watch cap. A short time later he felt a mild stinging sensation. He reported that very shortly the top of his skull became significantly numb, a felling that persisted for several hours afterwards. This incident came as quite a surprise to us, because we had been handling Conus halitropus with impunity never realizing that it possessed a stinging potential that could even mildly affect a human. Sometimes pure luck follows the ignorant !" 

 In a message on CONCH-L mailing list, 22 April 1997, Don Barclay from Pago Pago relates the following story of envenomation by a Conus geographus -

"Hi Conch-L'ers,

It seems like only last week (it was) that I asked (Chuck) a friend of mine, who has been diving nearly 50 years, whether he had ever been stung by a cone. He said no, that he had collected many, and had never been stung, but went on to relate a story of a friend who was diving off Wake or Midway Island and was stung by one that he had put in the sleeve of his wet suit. The guy made it to the shore, told his buddies, "This shell stung me," and died shortly afterward.

(However), after yesterday, my friend can no longer say that he's never been stung by a cone.

Right near the end of an early-afternoon dive, Chuck rolled a coral boulder just before he started his ascent from about 60 ft. Under the boulder, sure enough, was a cone, about 90 mm, that he recognized as a smallish geographus. He picked it up and put it in his thick mesh collecting bag, one of the tough ones with very tight mesh, that you'd think nothing could sting through. He then clipped it onto the diving harness on his chest, and started his ascent. On the way up, he felt a sting on his chest, which he first thought was a jellyfish. He looked down, and saw that the sting came from where the bag was, so he looked down at the bag to see if it could have been the cone. Sure enough, the geographus had crawled up toward the top of the bag (which was velcro-ed shut). He realized he had been stung through the bag, through a T-shirt, by this very active cone.

When I saw him yesterday evening about 6:00 he still felt fine, but had obviously been shaken by the sting. It didn't look too bad, about like a bee sting. On the drive home, however, he started feeling sick, and was quite sick during the night. Even today he was not feeling so great, and was still really weak. The good news is he survived a sting by a very venomous cone.

That brought a lot of questions to mind. Does the depth of the sting have a lot to do with how much envenomation occurs? It seems like it might. Does the fact that it was a small animal mean it was less dangerous? Are the radular teeth larger on a large cone? Significantly larger? Is the venom evenly distributed along the tooth, or is it more concentrated at the tip or base? Which cones are known to use their "harpoons" in self-defense, rather than in hunting food? Does a cone really have to be aggravated or provoked to cause such a reaction, or will some of them do it readily?

I've collected quite a few live cones, and I'm always careful with them even if they are not thought to be terribly venomous. This incident makes me doubt whether my thin gloves are really any protection against a cone intent on stinging something. Even five hours after he was captured, this little fellow was extremely active, crawling across the cement driveway, "feeling" for something to sting. I've never seen any other cone behave so aggressively. As I mentioned earlier, it was small for a geographus, about 90 mm, and quite red in color. It almost looked somewhere in between a Conus obscurus and geographus (at least the color made me think of obscurus), heavily coronated, with a flattish spire (definitely more like geographus than obscurus).

I'm sure there are several of you out there in Conch-L-land who can answer some of my questions, and responses would be appreciated. I am leaving for Tonga for a week tomorrow morning, so it may be after I get back before I get to read them. There are several replies available - see links (threads) on the CONCH-L web page at http://museum.nhm.uga.edu/CONCH-L/digest/COA1May1997/0067.html

Greetings from Pago Pago, handle those cones carefully!" 

'Diver Beware'... This Shell may KILL was the title of an article in the Australian NEWSLETTER of the Malacological Society, New Series No. 15, 31st October, 1971. In it he relates that "High on the list of dangerous marine invertebrates are the cone shells of the Indo Pacific regions. Recent history of some northern Australian cone shells show that stings from several species have resulted in severe illness and even death."

"Because of the availability of many Queensland cones, malacologists have been able to determine which species are the most dangerous. During these investigations the habits and life cycles of many species were recorded. Cones were shown to feed almost entirely on worms, other molluscs and or small fish. It is claimed that only those cones capable of killing fish can be judged as harmful to man. These include Conus geographus, Conus catus, Conus tulipa and Conus striatus."

"Due to a combination of fewer species and lack of publicly reported injuries, the life histories of many of the southern Australian cones are unknown. The few species that have been investigated feed almost exclusively on worms and therefore are not considered dangerous. Southern collectors in the past have not had to take any of the precautionary measures that their northern counterparts have, such as the use of gloves while collecting and the holding of cones ony by the posterior or thick end. In the future the southerners may also have to take a little care on one species at least."

"While diving and photographing molluscs at the Sir Joseph Banks group of islands off Fort Lincoln, South Australia, the author was fortunate enough to observe perhaps the first record of a southern cone shell actually in the process of devouring a fish. The specimens were found in 20 ft. of water under 2" of sand. Later identification showed the shell to be Conus segravei an uncommon species taken by divers along the southern coast from Victoria to Western Australia. When removed the fish was larger than the shell and, although the body had a rigid curved shape, there were no visible marks. Both specimens have since been deposited in the molluscan section of the Australian Museum" (in Sydney). A photo of the Conus segravei, Gatliff, 1891, (Seagrave's Cone) feeding on a fish accompanies the article and another photo of the same cone and fish taken from a different angle is in Neville Coleman's book "What Shell is That", URE Smith Press, ISBN 0 7254 0885 5, 2nd Edition 1988, Entry #550, p. 196.

Non-fatal stings in Brazil
In an article in 2006, Prof. Vidal Haddad Jr. from Motucatu, SP, Brazil raised the possibility that accidents caused by Conus could occur in Brazil citing the species Conus regius as a likely potential species. This was confirmed by a case reported in 2009. "A 42-year old male patient suffered an accident while scuba diving to look for shells on an intertidal rocky outcrop near Itapoan in the city of Salvador, State of Bahia, Brazil. The injury occurred around 10.00 am, after the victim had collected two Conus regius specimens. The handling procedure that the patient had been following for the specimens that he collected was to put the soft parts of the body under pressure in order to extract the operculum. After manipulating two specimens, he noticed a very small puncture in his right hand and felt a slight itching sensation, which was followed by local tingling and numbness. These symptoms later extended to the wrist and forearm, and after a few hours, he experienced paresthesia, numbness and mild difficulty in movement in his entire upper limb. There was no sensation of pain or any systemic phenomenon such as disseminated paresthesia, perioral tingling, alteration of consciousness or muscle palsy, etc. The heavy arm feeling remained throughout the day and had disappeared by the following morning, without leaving any sequelae."
References:
Haddad Jr V, Paula Neto JB, Cobo VJ (2006) Venomous molluscs: the risks of human accidents by Conus snails (Gastropoda, Conidae) in Brazil. Revista da Sociedade Brasileira de Medicina Tropical 39: 498-500.
Haddad, V. Jr., Coltro, M and Simone, LRL (2009) Report of a human accident caused by Conus regius (Gastropoda, Conidae). Revista da Sociedade Brasileira de Medicina Tropical 42: 446-448.[Article.pdf]

List of Conus envenomations :

John Singleton, cone shell guru of Geraldton, Western Australia, has been keeping account of reports of cone shell envenomations for many years purely out of curiosity. Here is his List of Envenomations (as of 29 March, 2000) drawn from the Australian Medical Journal, 1936; the Hawaiian Shell News (1960-1987); Sea and Shore, 1979 - and two witness accounts, one from Darwin, Northern Territory, Australia, 1996 ; the other from Exmouth, Western Australia, 1988.

Fatal Cases

(Prior to 1935) 

"The only fatal case (prior to 1935) of which definite information is available is the following, reported by Professor Cleland in the Sixth Report of the Microbiological Laboratory (New South Wales Government Bureau of Microbiology) for the year 1915. Professor Cleland quotes the following Reverend W. Wyatt Gill. On the island of Mare (southernmost of the Loyalty Group, immediately to the east of New Caledonia), in the doubtful light, a native "unhappily took a good-sized shellfish (Conus textile) and put it in his basket. He immediately felt a painful sensation running up his right arm to the shoulder. He went home. The pain increased until he writhed in agony The body swelled to an enormous size, and by daylight he was a corpse." 

Of the above cases, there were two caused by Conus aulicus and Conus tulipa, respectively, and these appear to be relatively mild ; two instances of poisoning by Conus textile, one mild and the other fatal ; and two of Conus geographus, one perhaps mitigated by treatment by incision and the other severe. 

(After 1935) 

"Early this year (1935) it was decided, at a conference held at Cairns, to form a Registry of Injuries Caused by Plants and Animals in Tropical Queensland, and accordingly questionnaires were forwarded to all the medical practitioners practising in North Queensland. The first case reported was by Dr. T.B. Clouston , then at Proserpine, to whom I am indebted for details of the fatal case here recorded." 

CONE SHELL MOLLUSC POISONING, WITH REPORT OF A FATAL CASE

 
Extract from The Medical Journal of Australia, April 4, 1936, page 464-466
By H. Flecker, M.B., Ch.M., F.R.C.S.,
Cairns, Queensland

HAYMAN ISLAND, June 27, 1935

C.H.G. , a male, aged twenty-seven years, whilst on a pleasure cruise landed at Hayman Island on June 27, 1935, and picked up a live cone shell (since identified by Mr. H.A. Longman, of the Queensland Museum, as Conus geographus). According to an eye-witness, it was gripped in the palm of one hand, with the open side downwards in contact with the skin, whilst with the other he proceeded to scrape with a knife, the epidermis, that is, a thin cuticle covering the hard part of the shell. It was during this operation that he was stung in the palm of the hand. "Just a small puncture mark
was visible,. Dr. Clouston did not see the patient until just before death, but the following details were obtained by him from the patient's mother, who was present with him. Local symptoms of slight numbness started almost at once. There was no pain at any time. Ten minutes afterwards there was a feeling of stiffness about the lips. At twenty minutes the sight became blurred with diplopia; at thirty minutes the legs were paralysed; and at sixty minutes unconsciousness appeared and deepened into coma.

No effect was noted upon the skin, lymphatic, alimentary or genito-urinary systems. Just before death, the pulse became weak and rapid, with slow, shallow respirations. Death took place five hours after the patient was stung.

A post mortem examination showed that all the organs, heart, lungs et cetera, were quite healthy. Mr. J.B. Henderson, Government Analyst, reports that no poison was found in the stomach contents. The victim was prior to the injury in perfect physical condition and in training for football.

The symptoms resemble much those of curare poisoning as described in earlier reports...."

Footnote: The identity of the victim "C.H.G." is revealed as Charles Garbutt from Townsville in the original article to be found in the Cairns Post 27/06/1935.


The article by Dr. Fletcher continues with some other interesting features of Conidae among which is mentioned that: 

Like Conus geographus, Conus marmoreus according to Montrouzier (Journal de Conchologie, Volume XXV, 1877, page 99), has likewise been known to inflict injury. According to Mr. H.A. Longman, a Japanese, F. Sugitana, in 1930 cites a case of poisoning by "Nubecula geographus" (as the species Conus geographus is also known), however the original publication (Venus, Tokio, Volume II, Number 3, 1930, page 151) has not been consulted by me (BGL) to date. 

Beware of Conus geographus and Conus textile
In addition to C.geographus, (12 fatalities reported prior to 1980), two other species, C.textile and C.marmoreus have been reported to kill humans, although the plausibility of these reports has been questioned on the basis of venom studies on dissected shells (Kohn, AJ "Cone shell stings". Hawaii Med. J. 17: 528-532, 1958] 

It appears that Conus textile (which is much more plentiful than Conus geographus) is to be highly respected. Numerous instances are quoted of the dread and respect which the natives of tropical seas show to this shell ; for example, the late Charles Hedley relates that while collecting on a coral reef he once rolled over a boulder and exposed a living Conus textile. Before he could pick it up, one of the natives hastily snatched it away, and explained, with vivid gesticulations, its hurtful qualities. On no account would he permit Mr. Hedley to touch it, but insisted on himself placing it in the bottle of spirits.

The identity of HGH is apparently Charles Gabett from Proserpine or Townsville (If you know, drop me a line).

So take care when next you are visiting the Great Barrier Reef and other tropical reefs. Don't pick up cone shaped shells with your bare hands no matter how pretty they appear.

Beware the killer snails - and take care out there !

Back to the nicotinic acetylcholine receptor

Table comparing lethality of conotoxin (from Conus geographus) with other known Venoms, Toxins and chemical agents in laboratory mice

BGL, June-95


 
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