Strongyloides, Dengue Fever, and Tuberculosis Conversions in New Zealand Police Deploying Overseas
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178
Strongyloides, Dengue Fever, and Tuberculosis Conversions in New
Zealand Police Deploying Overseas
Jenny T. Visser, MbCHB, MTravMed, Anantha Narayanan, and Briar Campbell, RN,
PGDipTravMed
Department of Primary Health Care & General Practice, School of Medicine & Health Sciences, University of Otago,
Wellington, New Zealand
DOI: 10.1111/j.1708-8305.2012.00601.x
Background. Members of New Zealand Police (NZP) deploy overseas in a variety of roles. There is limited published data on
travel-related morbidity in police as a subgroup of travelers.
Methods. An audit of pre- and postdeployment medical files for all NZP personnel deploying overseas during 2004 to 2010 was
undertaken. Of all deployments, 58.9% were within Oceania.
Results. Positive Strongyloides stercoralis serology was returned in 6.07% (95% CI: 3.80%–9.13%) at a rate of 9.00/1,000 person
deployment months (pdm) (95% CI: 5.57–13.8). Dengue fever seroconversion was recorded in 4.91% (95% CI: 3.40%–6.83%) at
a rate of 8.57/1,000 pdm (95% CI: 5.90–12.0). The relative risk of dengue infection was 7.47 for Timor Leste compared to all other
deployment destinations. An association between seroconverting for both dengue fever and Strongyloides was found. Tuberculosis
conversion was recorded in 1.76% (95% CI: 0.85%–3.21%) at a rate of 2.92/1,000 pmd (95% CI: 1.48–5.375). A single case of
human immunodeficiency virus (HIV) seroconversion was recorded. There were no recorded hepatitis C seroconversions.
Conclusions. Police deploying overseas appear to have similar rates of dengue and tuberculosis conversion as other groups of
travelers, and they appear to be at low risk of hepatitis C and HIV. Strongyloidiasis appears to be a significant risk; postdeployment
prevalence was markedly higher than that reported in a small number of studies.
A number of countries, including New Zealand (NZ),
deploy members of their police force overseas; as
such, they are a special group of international travelers.
of developing countries throughout the Pacific and
Asia (Table 1). Roles include peace keeping, advising
and mentoring local police, postconflict capacity
Only one published study reporting health risks in police building, and response to natural disasters.3 Length
deployed overseas has been identified.1 Considerably of deployment varies but is typically 6 months.
more data is published on military deployments,2 which As an employer, NZP has recognized that it has a
may share some similarities with police deployments. duty of care to minimize health risks associated with
New Zealand Police (NZP) personnel (both sworn overseas deployments; personnel undergo comprehen-
officers and non-sworn staff) deploy to a number sive pre- and postdeployment medical reviews including
testing for human immunodeficiency virus (HIV), hep-
atitis C virus, dengue fever virus, tuberculosis, and
Some of the data presented here was also presented as posters Strongyloides stercoralis. The rationale to screen for these
at the 12th Conference of the International Society of Travel particular diseases varies with respect to risk of infec-
Medicine Boston 2011. [Poster PO06.01 Tuberculosis conver- tion, future potential personal and public health impact,
sion in New Zealand Police personnel deploying overseas: A and feasibility of testing. Audit of these results will also
retrospective review. And PO06.02 Strongyloidiasis Incidence help rationalize predeployment health preparation and
(New Zealand Police International Services Group)—A Three in-country anti-infection strategies.
Year Retrospective Review.] Abstracts available at http:// The soil-transmitted helminth, S stercoralis, is
www.istm.org/Documents/Members/MemberActivities/ widespread in the tropics and subtropics.4 The helminth
Meetings/Congresses/cistm12/CISTM12-Poster- can autoinfect facilitating ongoing infection many years
Abstracts.pdf. post travel.5 Ongoing infection can cause considerable
Corresponding Author: Jenny T. Visser, MbCHB, morbidity5 and is a risk for disseminated disease
Department of Primary Health Care & General Practice, (with high case fatality rates) in those who are
School of Medicine & Health Sciences, University of Otago, immunosuppressed in the future.6 Personnel infected
Wellington, New Zealand. E-mail: jenny.visser@otago. can be offered treatment to reduce these health
ac.nz impacts.
© 2012 International Society of Travel Medicine, 1195-1982
Journal of Travel Medicine 2012; Volume 19 (Issue 3): 178–182Conversions in NZ Police Overseas Deployments 179
Table 1 Gender, nationality, and deployment location Any period of time spent continuously overseas was
counted as one deployment.
N (%) Disease-specific antibody serology tested for prede-
ployment exposure to dengue fever, HIV, and hepatitis
Gender
Males 598 (80.4)
C. Baseline tuberculosis status was determined by two
Females 146 (19.6) methods. Prior to 2007, tuberculin skin testing (TST)
Total 744 by way of a two-step Mantoux was used; from 2007, this
Nationality was replaced by a tuberculin interferon gamma assay,
New Zealand (NZ) nationals 663 (89.1) Quantiferon TB Gold (QFG).
Non-NZ nationals 81 (10.9) Dengue fever seroconversion was defined as a change
Total 744 from negative to positive dengue immunoglobulin G
Deployment location (IgG). A tuberculosis conversion was defined as either a
Solomon Islands 380 (51.1) Mantoux increase of 10 mm or more or a change from
Timor Leste 171 (23.0)
a negative to positive QFG assay. Strongyloidiasis was
Thailand (Phuket) 107 (14.4)
Bougainville 44 (5.9)
considered positive on the basis of positive serology
Afghanistan 27 (3.6) (IgG enzyme immunoassay).
Tonga 10 (1.3) Prevalence and comparative analysis was calculated
Pitcairn 3 (0.4) using OpenEpi software. Conversion rates were
Fiji 1 (0.1) calculated as per 1,000 person deployment months
Sudan 1 (0.1) (pdm). CIs for these estimates were calculated as follows.
Total 744 For proportions, Fisher’s exact CI was used; CIs for
rates were calculated using the Byar approximation to
the Poisson option; CIs for relative risks were calculated
The impact of dengue fever virus on international using Taylor series analysis.
travelers has been well documented, accounting for
hospitalizations,7 outpatient consultations,8 and being
Results
a major cause of fever, in returning travelers.9 Previous
infection with dengue fever virus is considered one risk During the study period, a total of 649 NZP personnel
factor for more severe disease with subsequent infections undertook 744 deployments to nine countries.
with different serotypes.10 Given this, a case can be Destination and demographic data are summarized in
made to establish past exposure before deploying to Table 1. The Solomon Islands was the most common
endemic areas. Screening for the infection caught while deployment destination, and the majority of those
on deployment will allow returning personnel to make deployed (80.4%) were males.
choices regarding future travel to dengue endemic areas. The prevalence and rates of conversions are sum-
International travel has been documented as a risk marized in Table 2. Positive Strongyloides serology was
factor for infection with tuberculosis.11 Early detection returned in 21 personnel. Comparing the two larger
of infection with tuberculosis can reduce future disease deployment destinations, the Solomon Islands had a
through treatment of latent tuberculosis.12 higher rate at 19.3/1,000 pdm (95% CI: 12.1–29.1)
Hepatitis C is an infection with a global distribution compared with 11.7/1,000 pdm (95% CI: 5.60–21.6)
but with higher prevalence in many developing in Timor Leste [a relative risk of 1.64 (0.78–3.47)].
countries.13 Behavior putting travelers at risk of HIV Personnel who seroconverted for dengue fever were
has been well documented14 and travel-related HIV 1.66 (1.15–2.32) times as likely to also have a positive
infections have been reported in returning travelers.15 or equivocal Strongyloides result (Table 3). Looking at
Early detection of HIV and hepatitis C infection is likely this from another angle, the rate of Strongyloides on
to have a positive impact on health outcomes. deployments where some returned dual positive results
was 48.3/1,000 pdm (95% CI: 20.8–95.3), while the
Methods Table 2 Conversions in New Zealand Police deploying
overseas
Seven years (2004–2010) of pre- and postdeployment
medical files of NZP personnel were audited. Dengue Rate/1,000 person
fever, HIV, hepatitis C, and tuberculosis results were Number Prevalence deployment months
available for the full period. Three years (2007–2010) of Disease converted (%) (95% CI) (pdm) (95% CI)
testing for infection with S stercoralis was also available.
[This was introduced after the description of a cluster of Strongyloides 21/346 6.07 (3.08–9.13) 9/1,000 (5.57–13.80)
Dengue fever 33/672 4.91 (3.40–6.83) 8.57/1,000 (5.90–12.0)
cases, including some NZP personnel, in the Regional
Tuberculosis 10/569 1.76 (0.85–3.21) 2.92/1,000 (1.48–5.38)
Assistance Mission to Solomon Islands (RAMSI).]1
HIV 1180 Visser et al.
Table 3 Strongyloides by destination While published work on travelers and strongy-
loidiasis has focused on two groups (immigrants from
Strongyloides rates (both endemic countries to developed countries16 and military
Deployment positive and equivocal)
destination n per 1,000 pdm (95% CI)
veterans5 ), it has been described in returning travelers in
two prospective studies.17,18 In one, 0.25% (at a rate of
Solomon Islands (SI)∗ 22 19.3 (12.1–29.2) 3.2/1,000 person months) were found to seroconvert for
Timor Leste (TL)∗ 10 11.6 (5.6–21.6) S stercoralis during short-term travel,17 and in another,
Afghanistan 2 24.6 (2.8–88.9) 0.8% of returning travelers had a positive S stercoralis
Bougainville 3 16.7 (3.4–48.9) polymerase chain reaction.18 These studies suggest that
Fiji 1 strongyloidiasis is a rare disease of returning travelers.
Pitcairn 1 The prevalence of S stercoralis infection (6.07%) found
Total 39 16.7 (11.9–22.84)
in this audit is therefore surprisingly high. A clear expla-
pdm = person deployment months. nation for this is not obvious. It is possible that NZP are
∗
Risk rate: SI : TL 1.6 (0.78–3.47).
deploying to areas with high prevalence (as the cluster of
cases diagnosed in the Solomon Islands might indicate).
rate on deployments that recorded no dual positivity Indeed, Solomon Islands-based personnel were shown
was 13.8/1,000 pmd (95% CI: 9.03–20.3). to have higher rates of Strongyloides-positive serology,
Twelve personnel [1.98% (95% CI: 1.08–3.35)] but positive results were not restricted to this destina-
tested positive for dengue fever prior to their first tion. While the literature suggests that Strongyloides is
deployment. Dengue fever seroconversion was recorded rare in travelers, what is not clear is whether more infec-
in 33 (4.91%) personnel (Table 2). Personnel deploying tion would be uncovered in if it was actively sought. The
to Timor Leste seroconverted at a rate of 23.7/1,000 results of this audit suggest that it might be a greater
pdm (95% CI: 15.19–35.28) compared to 3.20/1,000 risk than previously thought.
pdm (95% CI: 1.40–6.00) in those deploying to all Dengue infection has been recorded in up to 19.5%
other countries combined. The relative risk of Timor of a cohort of returning travelers,19 4.3% of aid
Leste compared to all other destinations was 7.47 workers,20 6.6% of military deploying to East Timor,21
(3.47–16.1). and in 7.7% of one US army unit in Somalia.22 The
During the audit period, 63 personnel had positive 4.9% (95% CI: 3.40%–6.83%) prevalence observed in
baseline tuberculosis giving a predeployment prevalence our audit was of the same magnitude as that observed
of presumed latent tuberculosis of 10.38% (95% CI: in these studies. The rate per 1,000 months exposed
8.07–13.08). Those who gave their nationality as being observed (8.57) is not dissimilar to that seen in Israeli
a New Zealander (and therefore more likely to be NZ travelers23 but is less than that described in Dutch short-
born) had a relative risk of 0.62 (0.33–1.17) for latent term travelers.24 The baseline 1.98% positive dengue
serology in our audit was similar to that found in a
tuberculosis.
German study.19 Because NZ is not endemic for any
During deployment, a tuberculosis conversion was
human flavivirus, positive baseline dengue was assumed
documented in 10 personnel (Table 2). Rates of
to represent past infection associated with previous
conversions were higher in those deploying to the
travel to, or residency in, endemic countries or a
Solomon Islands compared with Timor Leste; however,
cross-reaction to vaccination25 against other flaviviruses.
this was not statistically significant (Table 4).
In this audit, it was observed that those who had
There was one HIV seroconversion and no
seroconverted for dengue fever were more likely to also
recorded seroconversions for hepatitis C. Both had 0%
test positive for infection with S stercoralis. Why it is not
predeployment prevalence.
clear, it could be explained by personal attributes (are
those who are less fastidious with their insect personal
Discussion protection methods also less likely to take care to avoid
helminthic infections?) or environmental conditions (do
This is the first identified published audit of conversions conditions which favor one also favor the other?).
for Strongyloides, dengue fever virus, tuberculosis, HIV, Higher rates of dengue conversion were noted in
and hepatitis C in police deploying overseas. those deploying to Timor Leste, and while this is likely
Table 4 Tuberculosis conversions by country of deployment
Tuberculosis Total deployment Rates/1,000 person
Country conversions Total screened months deployment months 95% CI
Solomon Islands 8 307 1,998 4.01 1.72–7.89
Timor Leste 2 137 863.3 2.32 0.26–8.30
Other (Afghanistan, Bougainville) 0 125 — — —
Total 10 569 — 2.92 1.48–5.38
J Travel Med 2012; 19: 178–182Conversions in NZ Police Overseas Deployments 181
to reflect local disease patterns, it could be inflated tests, and readings are subjective.34 While there is sup-
by cross-reactivity to vaccination against Japanese port for the substitution of tuberculin gamma interferon
encephalitis,25 which is required for deployments to assays where TST has been traditionally used,35 some
Timor Leste and Thailand but not others. uncertainty remains around their sensitivity, specificity,
The observed 1.76% of NZP personnel converting and positive predictive value.36 Because many NZP per-
with tuberculosis compares favorably with that sonnel have received BCG vaccination as children and
published in a recent systematic review.11 The observed because pre- and postdeployment Mantoux testing was
rate of 2.9/1,000 pdm is more than that observed in the cause of most incomplete testing, it was decided
Peace Corps Volunteers26 but very similar to long-term that, despite limitations, QFG should be the preferred
travelers from Holland.27 test once it became available in NZ. It is recognized that
Of interest was the amount of latent tuberculosis both forms of testing may result in false positives causing
uncovered by baseline testing. Comprehensive data and overestimation of the prevalence of both latent tubercu-
an accurate incidence of latent tuberculosis in the NZ losis predeployment and infections during deployment.
population are lacking28 ; therefore, it is not clear if the
10.4% measured in this group is typical of the wider
NZ population. Conclusions
Data were not always complete. Despite a policy of NZP personnel deploying overseas are at risk of
having NZP personnel likely to deploy overseas in a con- travel-related infectious diseases. This audit revealed
stant state of readiness, it has not always been possible to positive Strongyloides serology, dengue seroconversions,
predict exactly who will need to deploy at short notice. and tuberculosis conversions during deployments, all of
The test most commonly missed predeployment was the which have future health implications. Some destina-
two-step Mantoux as this takes a minimum of 9 days to tions appear to carry a greater risk for specific diseases
complete. Postdeployment data were not always com- than others; in particular, deployment to Timor Leste
plete; 47 (6.3%) of all personnel failed to complete all or carried a significantly higher risk for dengue infection.
some postdeployment testing. The test most commonly A positive association between Strongyloides and dengue
lost to follow-up was the postdeployment Mantoux; this fever was observed.
improved with the introduction of QFG in 2007. While not all risk can be fully mitigated, predeploy-
If personnel had incomplete testing, their data were ment training and in-country strategies should continue
excluded from analysis. It is not known if those who did to focus on avoidance of insect- and soilborne dis-
not have time for full predeparture testing or failed to eases. This should include personal protection measures
complete postdeparture testing differed from those who (including insect proofing of work and living quar-
did. ters and use of repellents and permethrin-impregnated
An overestimation of strongyloidiasis is possible as clothing) and avoidance of skin contact with potentially
no baseline testing was done. The rationale is that NZ fecally contaminated soil. Future study should also focus
is considered non-endemic for S stercoralis29 with the on measuring the effectiveness of these interventions.
only published case reports of strongyloidiasis in New It would also seem reasonable to continue to screen
Zealanders being in persons born and traveling outside for these infections postdeployment so that future health
NZ.30,31 It is possible, however, that NZP personnel risks can be reduced, for example, by offering treatment
might have been exposed due to prior travel to, or for latent tuberculosis.
residence in, endemic countries. Also, in this audit, While the prevalence of dengue and tuberculosis was
screening was based on serology alone. For many years, of the same magnitude described in other travelers, the
isolation of the larva from fecal samples was considered higher than expected prevalence of S stercoralis infection
the ‘‘gold standard’’ of diagnosis, but techniques are (and a positive association with dengue conversion) was
difficult18 and some studies have shown low sensitivity.32 surprising. Further study, including optimal testing for
While serological tests have been quoted to have high strongyloidiasis in returning travelers, is warranted.
levels of both specificity and sensitivity,17 low sensitiv-
ity has been described in travelers.33 It would appear
that the diagnosis of S stercoralis infection, especially in Acknowledgments
returning travelers where worm burden might be low, is
not perfect. After discussion with local laboratories, the This audit was made possible due to sponsorship by
consensus was that, given the limitations of larval iso- the Wellington Medical Research Foundation (Inc)
lation, diagnosis would be made on serology alone and of a University of Otago summer studentship. Ethics
this might, in part, explain the high prevalence found. approval was granted internally by the University of
Screening tools for tuberculosis infection are lim- Otago.
ited. Both tuberculin skin tests and the newer tuber-
culin gamma interferon assays have their limitations. Declaration of Interests
TST can give false positives due to previous Bacillus
Calmette-Guerin (BCG) vaccination, previous exposure The authors state that they have no conflicts of interest
to non-human mycobacteria, the boosting effect of serial to declare.
J Travel Med 2012; 19: 178–182182 Visser et al.
References 19. Allwinn R, Hofknecht N, Doerr H. Dengue in travellers
is still underestimated. Intervirology 2008; 51:96–100.
1. Pattison DA, Speare R. Strongyloidiasis in personnel of 20. Jänisch T, Preiser W, Berger A, et al. Emerging viral
the Regional Assistance Mission to Solomon Islands pathogens in long-term expatriates (II): dengue virus.
(RAMSI). Med J Aust 2008; 189:203–205. Trop Med Int Health 1997; 2:934–940.
2. Aronson NE, Sanders JW, Moran KA. In harm’s way: 21. Peragallo MS, Nicoletti L, Lista F, D’Amelio R. Probable
infections in deployed American military forces. Clin dengue virus infection among Italian troops, East Timor,
Infect Dis 2006; 43:1045–1051. 1999-2000. Emerg Infect Dis 2003; 9:876.
3. New Zealand Police. New Zealand Police International 22. Sharp TW, Wallace MR, Hayes CG, et al. Dengue fever
Service Group. Available at: http://www.police.govt.nz/ in U.S. troops during operation restore hope, Somalia,
service/overseas. (Accessed 2011 Aug 18) 1992-1993. Am J Trop Med Hyg 1995; 53:89–94.
4. Genta RM. Global prevalence of strongyloidiasis: critical 23. Potasman I, Srugo I, Schwartz E. Dengue seroconversion
review with epidemiologic insights into the prevention of among Israeli travelers to tropical countries. Emerg Infect
disseminated disease. Rev Infect Dis 1989; 11:755–767. Dis 1999; 5:824–827.
5. Gill GV, Welch E, Bailey JW, et al. Chronic Strongy- 24. Cobelens FGJ, Groen J, Osterhaus ADME, et al. Inci-
loides stercoralis infection in former British Far East dence and risk factors of probable dengue virus infection
prisoners of war. QJM 2004; 97:789–795. among Dutch travellers to Asia. Trop Med Int Health
6. Marcos LA, Terashima A, Dupont HL, Gotuzzo E. 2002; 7:331–338.
Strongyloides hyperinfection syndrome: an emerging 25. Schwartz E, Mileguir F, Grossman Z, Mendelson E.
global infectious disease. Trans R Soc Trop Med Hyg Evaluation of ELISA-based sero-diagnosis of dengue fever
2008; 102:314–318. in travelers. J Clin Virol 2000; 19:169–173.
7. Stienlauf S, Segal G, Sidi Y, Schwartz E. Epidemiology 26. Jung P, Banks RH. Tuberculosis risk in US peace corps
of travel-related hospitalization. J Travel Med 2005; 12: volunteers, 1996 to 2005. J Travel Med 2008; 15:
136–141. 87–94.
8. Ansart S, Perez L, Vergely O, et al. Illnesses in travelers 27. Cobelens FGJ, van Deutekom H, Draayer-Jansen IWE,
returning from the tropics: a prospective study of 622 et al. Risk of infection with Mycobacterium tuberculosis
patients. J Travel Med 2005; 12:312–318. in travellers to areas of high tuberculosis endemicity.
9. Gautret P, Schlagenhauf P, Gaudart J, et al. Multicen- Lancet 2000; 356:461–465.
ter EuroTravNet/GeoSentinel study of travel-related 28. Lopez L, Sexton K, Heffernan H. Tuberculosis in New
infectious diseases in Europe. Emerg Infect Dis 2009; Zealand. Annual report 2009. Wellington: Ministry of
15:1783–1790. Health, 2010.
10. Beltramello M, Williams KL, Simmons CP, et al. The 29. Andrews J. The parasites of man in New Zealand: a review.
human immune response to dengue virus is dominated N Z J Zoology 1976; 3:59–67.
by highly cross-reactive antibodies endowed with neutral- 30. Powles AC. Strongyloides stercoralis hyperinfection: case
izing and enhancing activity. Cell Host Microbe 2010; 8: report. N Z Med J 1973; 77:169–171.
271–283. 31. Thomas MC, Costello SA. Disseminated strongyloidiasis
11. Freeman RJ, Mancuso JD, Riddle MS, Keep LW. arising from a single dose of dexamethasone before
Systematic review and meta-analysis of TST conversion stereotactic radiosurgery. Int J Clin Pract 1998; 52:
risk in deployed military and long-term civilian travelers. 520–521.
J Travel Med 2010; 17:233–242. 32. Johnston FH, Morris PS, Speare R, et al. Strongyloidiasis:
12. Horsburgh CR, Rubin EJ. Latent tuberculosis infection in a review of the evidence for Australian practitioners. Aust
the United States. N Engl J Med 2011; 364:1441–1448. J Rural Health 2005; 13:247–254.
13. Lavanchy D. Evolving epidemiology of hepatitis C virus. 33. Sudarshi S, Stumpfle R, Armstrong M, et al. Clinical
Clin Microbiol Infect 2011; 17:107–115. presentation and diagnostic sensitivity of laboratory tests
14. de Graaf R, van Zessen G, Houweling H, et al. Sexual for Strongyloides stercoralis in travellers compared with
risk of HIV infection among expatriates posted in AIDS immigrants in a non-endemic country. Trop Med Int
endemic areas. AIDS 1997; 11:1173–1181. Health 2003; 8:728–732.
15. Freedman D, Weld L, Kozarsky P, et al. Spectrum of 34. Garg SK, Tiwari RP, Tiwari D, et al. Diagnosis
disease and relation to place of exposure among ill returned of tuberculosis: available technologies, limitations, and
travelers. N Engl J Med 2006; 354:119–130. possibilities. J Clin Lab Anal 2003; 17:155–163.
16. Einsiedel L, Spelman D. Strongyloides stercoralis: risks 35. Centers for Disease Control and Prevention. Updated
posed to immigrant patients in an Australian tertiary guidelines for using interferon gamma release assays to
referral centre. Intern Med J 2006; 36:632–637. detect Mycobacterium tuberculosis infection—United States
17. Baaten G, Sonder G, van Gool T, et al. Travel-related 2010. MMWR Recomm Rep 2010; 59:1–25.
schistosomiasis, strongyloidiasis, filariasis, and toxocaria- 36. Menzies D, Pai M, Comstock G. Meta-analysis: new tests
sis: the risk of infection and the diagnostic relevance of for the diagnosis of latent tuberculosis infection: areas of
blood eosinophilia. BMC Infect Dis 2011; 11:84. uncertainty and recommendations for research. Ann Int
18. ten Hove RJ, van Esbroeck M, Vervoort T, et al. Med 2007; 146:340–354.
Molecular diagnostics of intestinal parasites in returning
travellers. Eur J Clin Microbiol Infect Dis 2009; 28:
1045–1053.
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