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Chapter 2: Working safely with Nipah virus

Risk assessment in field investigations - general principles
Safety procedures on Nipah-infected or suspected farms
Safety procedures in the laboratory with Nipah-infected or suspected samples

Nipah virus is classified internationally at the highest biosecurity level - BSL4 - and as such warrants the highest level of care in the field and laboratory. What precautions are necessary during investigations on farms where Nipah virus infection may be suspected? How should diagnostic specimens be handled in the laboratory where Nipah virus infections are suspected but not confirmed? How should sera from suspected outbreaks be handled? In addition to the discussion herein, it is recommended that a recent review of the principles of working safely during investigations of dangerous zoonotic agents (Abraham et al. 2001) be read.

Risk assessment in field investigations - general principles

A necessary prelude to any investigation of possible zoonotic disease is an assessment of possible risk to those involved in the investigation. The following approaches (from the CSIRO Australian Animal Health Laboratory’s Standard Operating Procedures for the Field Investigation of Animal Disease) are suggested:

Safety procedures on Nipah-infected or suspected farms

It is emphasized that precautions needed for working safely on farms extend beyond issues of personal protective equipment. Thought must also be given to appropriate work procedures to ensure that the activities of the investigation do not spread the infection, or increase the risk of exposure, to other locations. The following approaches are suggested (Daniels et al. 2000):

Figure 2: Protective equipment worn by those performing necropsies (note long sleeve overalls, double puncture-resistant gloves taped to overalls, and positive air pressure respirators)

Care of equipment

Safety procedures in the laboratory with Nipah-infected or suspected samples

Where Nipah virus infection is suspected as a possible differential diagnosis, appropriate protective clothing and safe work procedures should be adopted (Daniels et al. 2000).

Receipt of Blood Samples

Serum processing

Use standard operating procedures (SOPs) that utilize a step-wise diagnostic approach, with more dangerous procedures being undertaken only if the results of less dangerous screening tests indicate a need. Built into the SOP should be sampling strategies (for suspect outbreak and surveillance) to ensure that an adequate number of sera are collected, an adequate number of animals necropsied, and an appropriate range of tissues collected.

Laboratories should consider carefully what can be done safely with their facilities, and develop standard operating procedures that are written down, approved by senior management, and in which staff are regularly trained and retrained. Relevant recommendations for SOPs have been developed by several authors (Daniels et al. 2000; Nor & Ong 2000). A comprehensive discussion of diagnostic tests is presented in Chapter 4.

It is timely to suggest that veterinarians adopt a basic universal precaution approach to handling all animals and samples submitted to laboratories to minimize the risk of zoonotic disease. A basic requirement of such an approach is the prevention of exposure of the skin and mucous membranes to the body fluids of sick or potentially infected animals. Hence internal examinations and necropsies should not be conducted without gloves and other protective measures such as appropriate clothing and footwear. Depending on the circumstances, personal judgement should be exercised regarding the need for protection of the mucous membranes of the face and the need for respiratory protection.

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