Introduction
Globally, there are an estimated 1 billion people suffering from at least one of the
20 neglected tropical diseases (NTDs) prioritized by the World Health Organization
(WHO). Prevalent in tropical and subtropical regions, this group of NTDs comprises
diverse diseases, including vector-borne parasitic diseases (such as human African
trypanosomiasis [HAT], Chagas disease, and leishmaniasis), skin diseases caused by
environmental bacteria (such as Buruli ulcer [BU]), foodborne parasitic diseases (such
as taeniasis/cysticercosis) or snake bite envenoming, which—together with scabies
and other ectoparasites, mycetoma, and deep mycoses—were recently added to the list
[1]. Despite their differences, NTDs are synonymous with poverty, life-long disability,
stigma, and discrimination, not to mention the lack of effective control tools such
as vaccines, diagnostics, and drugs.
The majority of NTDs have been shown to worsen a patient’s mental health [2,3] in
different ways: (i) neurological—infection directly affects the brain, causing mental
disorders, such as in HAT, Chagas disease, and neurocysticercosis [4]; (ii) pain or
physical impairment—large skin ulcers in BU, blindness in onchocerciasis, and scrotal
swelling in lymphatic filariasis, all of which reduce the quality of life and increase
the risk of depression [5]; and (iii) stigma and social discrimination—NTDs are stigmatizing
due to their symptoms, e.g., skin lesions and disfigurement in BU, cutaneous leishmaniasis
(CL), or leprosy, as well as their association with poverty. All these factors are
related to impaired quality of life and have psychological consequences [6].
New initiatives, such as the Mental Wellbeing and Stigma (MWS) Task Group from the
Neglected Tropical Disease Non-Governmental Organization Network, are working to raise
awareness of psychosocial morbidity in patients and communities affected by NTDs [7].
The ultimate objective of the MWS group is to improve the care of both NTD patients
and their caregivers who are suffering or are at risk of suffering from mental health
issues. This line of action is crucial but would be considerably more effective if
complemented by preventive measures. Preventing NTDs in the first place will reduce
the risk of suffering from the mental health consequences associated with them. Alone
or in combination, the following interventions should be encouraged to control NTDs,
mitigate their impact, and promote well-being for affected communities [8]: (i) preventive
chemotherapy through mass drug administration campaigns (for soil-transmitted helminthiasis
and schistosomiasis); (ii) vector control (for Chagas disease, HAT, dengue, and chikungunya
virus); or (iii) providing safe water, sanitation, and hygiene (WASH) to control trachoma,
soil-transmitted helminths, and lymphatic filariasis.
In this Viewpoint, we suggest a complementary strategy to reduce the potential onset
of mental health disorders among NTD patients by advocating for early diagnosis and
therefore prompt treatment of these diseases. In NTDs, the development of neuropsychiatric
manifestations is usually associated with chronicity and late-stage disease. The parasites
causing HAT or Chagas disease only invade the central nervous system (CNS) in the
so-called second and chronic stages of the disease. Skin NTDs, such as BU, CL, or
yaws, often start as painless swelling or small nodules that eventually develop into
disfiguring and disabling ulcers if they are not treated early. Similarly, long-term
infections are associated with disability and chronic pain as experienced by patients
suffering from leprosy, lymphatic filariasis, and mycetoma or blindness in the case
of nontreated eye infections with bacteria (trachoma) and parasites (onchocerciasis).
The latter has also been associated with nodding syndrome, a neurological condition
causing progressive neurological deterioration and epilepsy in children. We argue
that treating NTDs as soon as possible after infection will reduce the risk of developing
neuropsychiatric disorders. Treatment in the early stage of disease requires prompt
access to correct diagnosis. In this paper, we present three examples showing that
developing and implementing better tools and strategies to diagnose NTDs could significantly
reduce their adverse impact on mental health.
HAT
HAT, or sleeping sickness, is a parasitic disease caused by protozoans belonging to
the species Trypanosoma brucei. The large majority of cases are caused by T. b. gambiense.
The disease has 2 consecutive stages: the first a hemolymphatic stage and the second
a meningo-encephalitic stage. In the first stage, trypanosomes invade the hemolymphatic
system, causing clinical signs and symptoms that are not specific to the disease (e.g.,
headaches or fever). If the patient is not treated, the trypanosomes invade the CNS
(stage 2), where they cause damage resulting in neuropsychiatric disorders (e.g.,
sleep disorders, derangement, or deep sensory disturbances). These syndromes are associated
with a strong stigma, which affects patients and impacts their health-seeking behavior
[9]. Diagnosing and treating HAT patients in stage 1 precludes the development of
mental health problems associated with stage 2. However, diagnosing HAT can be challenging
because the clinical signs and symptoms in stage 1 are not specific to the disease.
Until recently, diagnosis was conducted by specialized teams, often as part of large
active screening campaigns (teams of 10 to 15 people) or in a limited number of health
facilities, because case confirmation (usually compulsory to start treatment) requires
trained laboratory personnel. The development of rapid diagnostic tests (RDTs) to
screen for T. b. gambiense HAT [10,11] has enabled implementation of new control strategies.
First, RDTs can be deployed in primary healthcare facilities, enhancing the capacity
for passive screening for HAT [12]. Reducing the distance that a sick person has to
travel to get screened for HAT reduces the time from onset of symptoms to treatment
and allows diagnosing a significant number of HAT cases in the first stage of the
disease. In Kongo Central province (Democratic Republic of the Congo), for example,
65.4% of the HAT cases diagnosed in health facilities using RDTs were in the early
stage of the disease [13]. Second, RDTs allow implementing targeted active screening
using smaller teams (e.g., 1 to 2 people using motorcycles [14] to easily cover distances).
These new active screening strategies (door-to-door) are more efficient than active
mass screening in low-prevalence settings [15] and are currently being implemented
using RDTs in Guinea, Côte d’Ivoire, and Chad. Clearly, diagnosing HAT patients earlier
improves the outcome of their treatment and contributes to the control and elimination
of the disease in endemic countries.
CL
CL is one of the clinical forms of leishmaniasis, a group of diseases caused by a
protozoan of the Leishmania genus. Although CL is not lethal, it causes chronic and
disfiguring skin lesions, leading to well-documented psychosocial morbidity in affected
individuals [2,3]. The impact of CL on the mental health of the patients depends largely
on the type and location of the lesions [16], particularly for women and young girls
if the lesions occur on the face [17]. Early treatment prevents the enlargement of
the scars and disfigurement, as well as the risk of developing mucocutaneous leishmaniasis,
a secondary form of CL that causes significant tissue destruction. This form is endemic
in some areas, such as South America. Because treatment for CL is toxic and painful,
it should only be initiated after a confirmatory diagnosis has been made. However,
CL diagnosis is still based on demonstrating the presence of Leishmania parasites
by direct microscopy of Giemsa-stained smears made using skin scrapings or fine needle
aspirates obtained from lesions. This approach reduces access to diagnosis and treatment
at reference health facilities, such as district hospitals in endemic countries. In
Afghanistan, for example, where almost 30,000 CL cases were reported in 2015, CL patients
from rural areas had to travel to the reference leishmaniasis clinic in Kabul for
diagnosis and treatment. The lack of diagnostic capacity in peripheral health facilities
severely delays or precludes access to care for patients, leading to chronic skin
lesions, reduced function, disability, stigma, and mental health problems.
An RDT for the detection of Leishmania in CL skin lesions is now available: the CL
Detect Rapid Test (InBios International, Seattle, WA). This RDT allows diagnosing
CL in primary healthcare facilities as it only requires obtaining a sample from the
lesion using a small dental broach; the results are available in less than an hour
and can be interpreted the same way as results from a malaria RDT. As shown in different
studies, the specificity of the CL Detect RDT is good, but its sensitivity is low
[18–20]. Nevertheless, the CL Detect can significantly improve access to CL diagnosis
in endemic regions. Based on its performance, people showing signs of having CL and
who then test positive using the RDT in peripheral health facilities should start
treatment without delay. Those who test negative still need to be referred for confirmation
of either being positive or negative [19]. Better diagnostic tests for CL should be
developed [21], but we must maximize the use of the tools already available, in particular,
the CL Detect RDT, to improve access to CL care and reduce the mental health sequelae
associated with CL in endemic countries such as Afghanistan.
BU
BU is an important public health problem among rural communities in several countries
in sub-Saharan Africa, where it mainly affects children under 15 years of age. As
with several other NTDs, BU initially presents as small, nonspecific, painless swellings
that, without treatment, eventually ulcerate and enlarge into disfiguring sores that
cause long-term functional disability in up to 25% of cases. With the majority of
cases impacting children, patients typically have to be accompanied by family members
during several weeks of hospitalization, which has a negative effect on household
earnings and leads to many patients being abandoned in hospitals or withdrawn from
treatment. Patients with large ulcers or cured people with disfigurement often become
socially excluded through negative attitudes in the community and end up dropping
out of school or from the workforce [22]. Early and accurate diagnosis and antibiotic
treatment are highly effective and therefore minimize the suffering, disability, and
socioeconomic burden of the disease. Thus, it is crucial to have a radically improved
diagnostic test that can make decentralized early diagnosis possible [23].
Although current diagnostics for BU are expensive and inappropriate for poor, rural
settings, significant progress has been made in recent years. Simple molecular amplification
methods, such as the loop-mediated isothermal amplification (LAMP), are now available
for BU diagnosis [24]. However, even if these tests are easier to perform than PCR,
they still require basic laboratory infrastructure. To allow BU diagnosis at primary
healthcare facilities in endemic regions, efforts have been concentrated in developing
an RDT to detect mycolactone, an exotoxin produced by Mycobacterium ulcerans in BU
lesions [23]. Promising preliminary results of a prototype RDT to detect mycolactone
were presented at the WHO meeting on “BU and skin NTDs” held in Geneva from 25–27
March 2019. This point-of-care test will enable the identification of the disease
in its early stages at community or primary healthcare facilities where the at-risk
populations live. As for CL, early diagnosis and treatment of BU patients will limit
the extent of the skin lesions, disability, and stigma, thus significantly reducing
the adverse impact on mental health.
Conclusion
The links between poverty, mental health, and NTDs are well established (Fig 1). Preventing
NTDs, ensuring prompt access to diagnosis and treatment of NTDs, and improving care
of those suffering from the psychological consequences of these diseases should be
part of a holistic approach to break the existing vicious cycle of disease—lack of
diagnosis, lack of treatment, and deterioration. As illustrated by the previous examples,
the efforts to improve diagnosis of NTDs should be made at different levels: research
and development (e.g., RDT for BU), evaluation (e.g., RDT for CL), and implementation
(e.g., RDT for HAT). The burden of neuropsychiatric disorders, particularly for NTDs,
is sadly underestimated [2]. Thus, even if the impact of prompt diagnosis of NTDs
in preventing mental health disorders remains to be evaluated, we can foresee that
it is significant.
10.1371/journal.pntd.0007679.g001
Fig 1
Poverty, NTDs, and mental health cycle, plus areas of intervention.
1MWS group objectives: “(i) to support and develop resources for advocacy of affected
individuals and to promote their empowerment; (ii) to ensure NTD programmes include
interventions which promote positive attitudes and behaviour of communities to those
affected and address structural discrimination; (iii) to promote self-advocacy and
expression of the needs of those affected; and (iv) to increase the awareness of the
rights and responsibilities of those affected and those who provide services to them,
including their caregivers” [3]. MDA, mass drug administration; MWS, Mental Wellbeing
and Stigma; NTD, neglected tropical disease; WASH, water, sanitation, and hygiene.