Epidemiology and Infection
cambridge.org/hyg
Giardiasis: a diagnosis that should be
considered regardless of the setting
Angel A. Escobedo1,2, Pedro Almirall3, Kurt Hanevik4,5, Sérgio Cimerman6,
Commentary
Cite this article: Escobedo AA, Almirall P,
Hanevik K, Cimerman S, Rodríguez-Morales AJ,
Almanza C, Auza-Santivañez J (2018).
Giardiasis: a diagnosis that should be
considered regardless of the setting.
Epidemiology and Infection 146, 1216–1218.
https://doi.org/10.1017/S0950268818001504
Received: 13 February 2018
Revised: 9 May 2018
Accepted: 14 May 2018
First published online: 11 June 2018
Key words:
Giardia; giardiasis; travel medicine
Author for correspondence:
Angel A. Escobedo,
E-mail: escobedo@infomed.sld.cu
© Cambridge University Press 2018
Alfonso J. Rodríguez-Morales2,7, Caridad Almanza8 and
Jhossmar Auza-Santivañez9
1
Academic Paediatric Hospital ‘Pedro Borrás’ La Habana, Cuba; 2Working Group on Zoonoses, International
Society for Chemotherapy, Aberdeen, UK; 3Municipal Centre of Hygiene, Epidemiology and Microbiology ‘Plaza’, La
Habana, Cuba; 4Norwegian National Advisory Unit on Tropical Infectious Diseases, Department of Medicine,
Haukeland University Hospital, Bergen, Norway; 5Department of Clinical Science, Faculty of Medicine, University of
Bergen, Bergen, Norway; 6Institute of Infectious Diseases ‘Emilio Ribas’, São Paulo, Brazil; 7Research group Public
Health and infection, Faculty of Health Sciences, Universidad Tecnológica de Pereira (UTP), Pereira, Risaralda,
Colombia; 8Central Clinic ‘Cira García’, La Habana, Cuba and 9Academic Clinical and Surgical Hospital ‘Calixto
García’, La Habana, Cuba
Abstract
Although Giardia, the aetiological agent of giardiasis, is one of the most prevalent intestinal
parasitic infections world-wide, for industrialised countries, it is mainly appreciated as an
imported disease with the minimal local transmission. However, the current evidence challenges this perception; Giardia has relevance beyond the high prevalence areas. This infection
may be asymptomatic or cause gastrointestinal complains and long-term sequelae, including
irritable bowel syndrome, chronic fatigue and impaired child growth and cognitive development. Its detection and diagnosis present a challenge to physicians who may not be familiar
with this infection. To improve interventions to control this parasitosis, it is necessary to
maintain a high index of suspicion and remain vigilant in finding cases at risk for infection.
A better understanding of the characteristics of populations importing infections alongside
improved methods to reliably classify infections as imported or acquired locally will help to
ensure early and accurate diagnosis. The evidence shows that public health problems like giardiasis are global issues that need to be addressed collectively by both high and low prevalence
countries.
We welcome the paper by Currie et al. [1], in which they emphasise the need for significant
improvements around Giardia selection criteria and testing algorithms in their country and at
international level. Their work is a valuable example which alerts readers about the necessity of
considering Giardia infection also in low-prevalence settings.
Giardia is estimated to cause annually 184 million clinical cases [2] and an associated 171
100 (115 777–257 315) disability-adjusted life years [3]. In industrialised countries, where the
incidence of human giardiasis, the disease that Giardia causes, decreased after improvements
of sanitary infrastructures and safe drinking water, it is seen to be principally associated with
travelling to – or immigration from – endemic areas. As highlighted by Currie et al. many
reports are challenging this perception [4–12]. Indeed, this disease is being increasingly considered as a re-emerging disease because of its recognised role in numerous outbreaks of diarrhoeal diseases in daycare centres and also due to water-borne associated outbreaks [13]. In
industrialised countries, there are also deprived communities and groups in the population
exposed to suboptimal hygienic conditions, placing them at increased risk of diarrhoeal disease
[5, 8, 9]. This facilitates human to human transmission and also allows travel-acquired Giardia
to spread more easily within these countries, a mechanism termed introduced autochtonous
transmission. The routes of transmission are responsible for a substantial proportion of
both diagnosed and undiagnosed giardiasis cases. For instance, in Germany, of 273 interviewed cases of giardiasis, 131 (48%) of cases were not associated with travelling abroad [6].
Additionally, untreated drinking water has been identified as a risk factor for sporadic giardiasis in New Zealand [14]. Swallowing water while swimming in pools, recreational fresh water
contact, drinking treated tap water and eating lettuce had positive and independent associations with infection in a case-control study carried out in residents who had not recently travelled outside the UK [4], pointing out the possibility that even treated tap water is a source of
sporadic giardiasis. Recently, Adam et al. analysed data on all giardiasis outbreaks reported to
the US Centres for Disease Control and Prevention for 1971–2011, describing and highlighting
the ability of this protozoan to cause outbreaks through multiple transmission routes [11],
including waterborne (74.8%), foodborne (15.7%), person-to-person (2.5%), animal contact
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https://doi.org/10.1017/S0950268818001504
1217
Epidemiology and Infection
(1.2%) and unknown (n = 14, 5.8%) transmission. Transmission
from ill children to household contacts has also been documented
in outbreak investigations [15] and sexual activity, mainly in men
who have sex with men, which results in faecal–oral contact can
lead to transmission of Giardia [16].
There are several factors hampering the rapid diagnosis of
Giardia infection in industrialised countries. Firstly, as in developing countries, a large proportion of infected people do not
develop symptoms but may shed Giardia cysts for a period of
time [17, 18]. Secondly, in individuals who do develop symptoms,
detection depends on clinical experience, technical skills and on
available diagnostic resources [19]. These may vary widely
between and within countries. Giardiasis may, therefore, go
undiagnosed or may be treated inappropriately by physicians
who are unfamiliar with this disease. According to a few studies
carried out in developed countries [20, 21], physicians who see
Giardia-infected individuals often lack the experience and awareness of the disease. For example, the American College of
Obstetricians and Gynecologists in collaboration with the
Centres for Disease Control and Prevention made a survey of
obstetrician-gynecologists on their clinical and epidemiologic
knowledge of giardiasis in pregnancy [20]. Good general knowledge about diagnosis, transmission and prevention was found.
However, difficulties concerning the best way to treat this parasitic
infection during pregnancy were identified [20]. In a survey of US
pediatricians evaluating their knowledge and perceptions on the
treatment of giardiasis in children, only 10% indicated they
would suspect parasites in a patient with diarrhoea lasting more
than 1–2 weeks [21]. History and physical exam (83.9%) and duration of diarrhoea (74.4%) were the main clinical aspects for
parasitic-induced infection, with about one-third (36.2%) only
taking into account the possibility of intestinal parasites when
all other possible causes had been ruled out. Other studies have
shown that a significant number of patients with giardiasis had
encounters with health professionals without the diagnosis
being considered, given the frequently observed delay between
the onset of illness and diagnosis [22–25]. Surprisingly, in one
study, 10% of patients reported receiving drugs, such as ciprofloxacin, which is ineffective against this protozoan [25]. The discovery of Giardia as the cause of a large waterborne outbreak in
Bergen, Norway was delayed due to no history of travel abroad
among the many patients seeking medical care for diarrhoeal disease [24]. These scattered reports underline the need to enhance
efforts to provide education among general practitioners and
pediatricians to be aware of Giardia as a cause of indigenous
cases of diarrhoea and on how best to diagnose and effectively
treat them.
Additionally, faecal specimens are often not routinely
requested from persons with diarrhoeal illnesses [26, 27]. If
Giardia is suspected, the right specimen and specific tests must
be ordered and sent to a laboratory where adequate diagnostic
tools and skills are available [28]. For laboratory diagnosis, a morphological determination by microscopy is the most commonly
used method [29], which is simple and fast. Unfortunately, it is
less sensitive, requires multiple sample examinations and concentration procedures and needs to be performed by well-trained
technicians. Additionally, as it requires multiple clinic visits, it
may be associated with high rates of diagnostic drop-out. In
some industrialised countries, innovative modern technology
has replaced microscopy as a routine diagnostic tool; i.e. the use
of multiplex polymerase chain reaction assays for the detection
of Giardia and other gastrointestinal protozoan pathogens (that
could be simultaneously present) is particularly valuable. It assists
in detecting the true prevalence of Giardia as well as earlier detection of outbreaks if performed on a broader array of patients with
diarrhoea.
Finally, the awareness of the community is low. In one study
caregivers of children with diarrhoea and more specifically persistent diarrhoea induced by Giardia showed that relatively low
proportions of caregivers had heard of Giardia (36%) [30].
There are important reasons to pay attention to underdiagnosis of Giardia infection. In some cases, Giardia can cause
severe clinical manifestations such as acute and chronic diarrhoea
(the latter defined in case of episodes lasting more than 4 weeks)
[31]. This infection may also be accompanied with or without
malabsorption, abdominal cramps, nausea, vomiting, increased
flatulence and weight loss [32]. Additionally, a range of extraintestinal manifestations and long-term consequences have been
identified and associated with this protozoan infection [33]. A
controlled prospective study of a cohort of individuals who had
confirmed Giardia infection during a waterborne outbreak
found a significantly increased risk for post-infectious irritable
bowel syndrome and chronic fatigue even 6 years after the infection [34]. Of interest in both high and low prevalence settings,
two recent studies have shown that early exposure to- or persistent
Giardia infection during first 6 months of life, even if asymptomatic, contribute to increased intestinal permeability and to stunted
growth at 2 years of age [35, 36].
The changing perspectives of the incidence and prevalence of
giardiasis in industrialised countries, where it is still relatively
neglected and underappreciated by practicing clinicians and
maybe by caregivers, need to be taken into account. Giardiasis
may exceed the current prevalence estimates. An increased awareness for indigenous transmission is hoped for and as a result, indications for Giardia testing would not be only done in returning
travellers, nor considered only in a chronic diarrhoeal disease
context. This might avoid delays in diagnosis.
Currie et al. [1] study reminds us that there are multiple
potential areas for improvement in laboratory testing algorithms
and diagnostic awareness of giardiasis. The evidence shows that
public health problems like giardiasis are a global issue that
needs to be addressed collectively by industrialised and developing countries. This protozoan disease, as well as other enteric
parasites, should be considered more often in the differential
diagnosis. It should be on the clinical, epidemiological and public health agenda, to be carefully addressed, for better decisionmaking in public health policies. It is especially important to
keep in mind that, as in most infectious diseases, ‘what goes
around, comes around’.
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