**6. Challenges to epidemiological surveillance**

**5. Challenges to entomological surveillance**

100 Dengue Fever - a Resilient Threat in the Face of Innovation

location.

transmission still persists [19–21].

services, climate, etc. [22–27].

Entomological surveillance has been employed to (1) determine changes in the geographical distribution of *Ae. aegypti*, (2) obtain relative measurements of *Ae. aegypti* populations through time and identify areas of "high" infestation or periods of growth in vector populations and (3) evaluate the impact of anti-vector interventions. These indicators cannot be used straightforwardly to estimate the risk of virus transmission in the population at a certain time or

*Entomological indexes*: There are various indicators (indexes) and methods to detect or monitor *Aedes* populations (egg, larval, pupal and adult stages) in relation to their location (containers, home or geographical area). The indicators were initially qualitative (negative/positive breeding sites or houses) and evolved toward being quantitative in order to identify the number of mosquitoes, though without specifying density, productivity or breeding site relevance

One element of the evolution of control programs has been the slow innovation of entomological monitoring indicators, an area dominated by the traditional *Stegomyia* indexes used in the campaign to eliminate *Ae. aegypti* in the fight against yellow fever: house (HI), container (CI) and Breteau (BI) indexes. These indices were useful in the extent to which they indicated the (qualitative) presence and absence of the vector in a campaign that sought its elimination and attempted to evaluate the endeavors toward physical elimination of breeding sites (positive breeding sites or houses). The focus now turned toward the reduction in density (rather than the elimination) of the vector, and these indicators have lost their usefulness [15, 16].

The need for better indicators led to indices of pupae and oviposition, closer life stages to the ideal measure of adult (female) mosquito populations, which would allow for a better approximation of the estimated risk of transmitting dengue [17, 18]. These indicators of entomological risk did not reduce or eliminate the challenges to evaluate the interventions because the need to relate density and/or the threshold of the different vector stages to risk of

The use of "nonentomological" (though associated with infestation and facilitators of vectorhuman contact and epidemiological risk) indicators has also been proposed and ought to be considered in order to better understand the dynamics of dengue transmission—for example, density and distribution of human populations, socioeconomic conditions, living and public

The selection of indicators and surveillance methods depends on the objective of surveillance (density reduction, risk detection and outbreak prevention), the levels of infestation and the capacity for implementation. Nevertheless, there is little evidence showing that the control programs employ systematic monitoring of vector populations—in particular, monitoring of adult females—in order to measure infestation and risk of dengue transmission [18, 28, 29]. In the best of cases, programs still employ indices of infested sites/breeding sites [29, 30] in order to establish "areas" of transmission risk without demonstrating the predictive capacity

of these indices as indicators of dengue transmission risk in the last 50 years [31].

(cryptic). The indices are not sufficiently exact to identify the risk of transmission [14].

The evaluation of interventions to control *Ae. aegypti* faces diverse challenges regarding the potential impact they may have on the risk of transmission not only of dengue but also of other arboviruses recently associated with the region's epidemiological profile: Zika, chikungunya and yellow fever. The first challenge is estimating the impact derived from the disease that may be affected and the second in measuring the direct impact of the interventions on the vector populations in all of their stages and their relation to transmission risk (vectorial competence and capacity).

Systems of epidemiological surveillance now have the task of measuring, in the most precise manner possible, three infections transmitted by *Ae. aegypti*. Now things are complicated because the syndrome of fever and exanthema may be indicative of dengue, Zika and chikungunya. The diseases are also associated with other signs, distinctive symptoms and highly specific clinical complications (hemorrhages with severe dengue, chronic arthralgia with the chikungunya virus and congenital syndromes and neurological complications with Zika).

The estimate of the actual number of dengue cases, and now of Zika and chikungunya, is very difficult to calculate due to *biological problems* inherent to the infection, such as the number asymptomatic infections, or of unspecified fevers, which hinders the correct quantification of the impact of each of these illnesses. Clinical confusion regarding symptomatic fever/exanthema and discriminating diagnosis is reduced when complications are severe and chronic manifestations of each infection are observed. The *operational problems* are evidenced through the low demand of health services—especially during outbreaks—which results in under registration of cases when the person does not demand or lacks access to health services, medicates himself or opts for treatments of symptoms they already recognize through previous exposure to the problem.

selected sites until the detection of evidence of the sustained impact and the reduction of potential risks of evolution in the manipulated species and introduced genetic or biological marker. It is believed that innovations would be used in places where traditional measures of control have little to no effect and where they may have an important epidemiological impact on transmission dynamics. However, as with any intervention—and especially with innovative interventions—there are some operational changes that will need to be considered for the

Challenges for the Introduction and Evaluation of the Impact of Innovative *Aedes aegypti*…

http://dx.doi.org/10.5772/intechopen.79862

103

*Integration of interventions by level of application:* A central element is the organization of interventions by level of application. We must keep on with simple practices, such as domestic hygiene (personal level); routine broad procedures such as breeding sites elimination campaigns; technically elaborated entomological sampling and larvicide application (community level); and even specialized, high-cost actions that require equipped, professional personnel, such as insecticide sprays (town level) or programs of medical attention for the correct handling of severe cases (national level). On the other hand, interventions aimed at urban infrastructure (access to potable water, garbage collection and a recycling system) ought to be incorporated bearing in mind that require high-level political commitment and substantial

An additional challenge is the integration of abovementioned interventions in order to perform them in a combined and sequential manner and differential intensity in accordance with the epidemiology of each area vulnerable to transmission. Although the available human and financial resources will generally define this, we must pursue on the objective to direct efforts to high-risk areas. The selection of localities in which to introduce these innovations for control should take into account the degree of risk in that area as well as the impact produced by

*Program structure*: The organization of the control programs has evolved from a vertical centralized structure ("Top-down")—independent of health services and with a "militarized" organization—to a more horizontal and decentralized structure, more tightly linked to services of surveillance and medical care and more participatory ("Bottom-up"). The advances toward a horizontal organization are variable, and in many programs, there exists a combination of both structures, in which the coordination is centralized. The need of coordinating all these processes—including the application of GMM/BCMW-based strategies—implies that programs that adopt these innovations ought to incorporate a centralized perspective, although the host communities ought to participate in the operational unfolding of the new

*Implementation*: The traditional control programs have an established procedural routine repeated each year, in the same season, with the same resources (human resources as well as physical, chemical and biological); however, the areas of control must be expanded and the actions intensified due to the increase in at-risk zones. In the case of IVM, it has been proposed that actions implemented should be differential in frequency and intensity in accordance with

*Human resources and operational infrastructure*: The vertical focus of traditional control programs developed a whole line of training for technical vector control personnel totally apart from promotional, preventative and educational health activities. This operational personnel was

programs of control with *Wolbachia* and GMM.

investments (municipal level).

the illnesses.

technologies.

epidemiological risk.

Only patients with severe symptoms go to the doctor, and these are the best detected by the surveillance system. An additional operational problem is the lack of sensibility to clinical diagnoses of fever and the limited collection of samples in order to confirm diagnosis—even during an epidemic—now that normative processes restrict the collection of samples to only severe cases or those at the onset of an outbreak. Only those cases confirmed by diagnostic methods available in regional labs (serology and viral isolation) are recorded [33].

These circumstances impact the opportunity for vector control interventions (operational problem) since the presence of asymptomatic cases and unspecified or febrile patients are not registered early, and it is not until the accumulation of many cases that an increase in transmission is detected; it is at this point that control actions are initiated [34]. Among the *cultural problems*, or problems of perception, we find the familiarity with the sickness and its management given prior experience; fever is not considered an important risk to one's health and does not merit a visit to a doctor unless accompanied by more serious symptoms.

*The necessity of improving detection, diagnosis and notification*: Epidemiological surveillance of arboviruses faces two importance problems that occur in two different spaces: the community and health services. Given the clinical characteristics, an important number of cases do not demand health services due to their asymptomatic status or the unspecified fever that does not merit a visit to a doctor. Even many clinical cases do not consult medical services due to the patient having recognized and identified the case and knowing how to treat it. Due to this situation, we underestimate the number of cases and the detection of the illness and detection for those affected should be improved [35, 36].

In the health services sector, diagnosis and documentation related to cases should be improved by strengthening the capacities of health personnel and local laboratories. To accomplish this, the following are indispensable: (1) counting on clinical guidelines that facilitate the health personnel in the identification and treatment of clinical cases under surveillance (dengue, Zika and chikungunya) and that reduce the identification of false negatives, (2) establishing criteria for the collection of samples and having the supplies necessary for serological and/or viral confirmation of suspected cases, (3) improving the reporting of cases unconfirmed in the laboratory (probable/suspected) following the algorithms of differential diagnosis for the three illnesses, (4) encouraging the reporting of cases by epidemiological association in the case of an outbreak and (5) seeking mechanisms for notification of cases identified by private medical services [37].
