Abstract

Tick bites represent a significant problem on offshore wellhead towers for the company and its contractors. Over 50 cases per year were reported from one supercomplex alone over a 5 year period.

The health risks to employees are tick bite reactions (including blistering, ecchymosis and gangrene), tick bite paralysis (beginning around 2 days after the bite with weakness in the lower extremities, progressing to falling episodes and incoordination), and tick borne infections (eg Crimean-Congo haemorrhagic fever, the last outbreak in the UAE having a mortality of over 70%).

The ticks were mainly carried by the Socotra cormorant, a migratory bird protected by law.

The approach taken to reduce the incidence of tick bites was to try to reduce the occupancy of the sites by the birds, to reduce the level of faeces containing bird ticks, to reduce worker stay times, and to provide appropriate personal protective equipment.

Bird scaring devices were ineffective and the use of wires would have presented a safety hazard to helicopter operations. Tactile repellents would be ineffective because of the usage of the towers leading to its rapid removal.

Manual cleaning, steam cleaning and grit blasting to clear bird faeces carried increased health risks to the employees carrying out the work which would have had to be frequently repeated given the speed at which the ticks return following cleaning.

The use of insectides would have had an adverse environmental impact and, as with cleaning, would have to be rereated frequently.

Stay times were reduced and instructions given to reduce exposed skin areas by more effective use of overalls. A system of treating overalls using permethrin was developed utilizing onshore laundries given the space limitations of offshore laundry facilities. DEET based insect repellants were also provided. Over a two year period the number of reported cases has reduced by 50%.

Introduction

Tick bites have been a problem on certain offshore sites within the Arabian Gulf for some years. In 1982 a paper published in the Lancet noted that petroleum industry workers bitten by a tick found on marine birds were admitted to hospital for about two weeks with bullae at numerous bites sites, intense pruritis and fever[1].From 1998 to 2002 on one of ADMA-OPCOs assets off the coast of the United Arab Emirates there was an average of 50 reported tick bite cases per year related to work on Wellhead Towers. Many of these cases had severe skin reactions and some required transfer to onshore facilities for further treatment. Concern had also been raised regarding the risk of tick borne infectious illness, including Congo Crimean haemmorhagic fever (reported outbreaks in the United Arab Emirates have had mortalities of from 63% to over 70%[2,3]), Alkhurma Virus Infection, Relapsing Fever and Erlichosis, and from tick bite paralysis. A systematic plan utilizing best practice and the hierarchy of controls was developed to address this problem.

The "vectors"

The main vector for the ticks was the Socotra Cormorant (Phalacrocorax nigrogularis), a protected seabird which commonly roosted on the towers.The species is recognized to be globally threatened and up to a third of the world population (650,000–1,000,000) can be present in UAE waters. During a study carried out in 2001 numbers of 200 to 300 plus were observed on some of the towers the predominant ticks observed identified were Ixodidae (hard bodied ticks). More recent work has shown significant numbers of Argassidae (soft bodies ticks).

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