1. Closing in on the reservoir:
pro-active case detection as a strategy to contribute to Plasmodium falciparum elimination in an area of multidrug resistance in Cambodia
MSF in Chey Saen District
Preah Vihear Province – Cambodia
Gabriele Rossi
Research Coordinator MSF OCB Cambodia
London Scientific Days,
May , London
New strategy within the effort/endoavour of contributing to eliminate Pf in an area of artemisinine resistance in Camboida.
Cambodia is one of the 5 countires of the GMS where AR was discovered in Today in GMS ACTs are failing to various degree, driven by AR, and in Cambodia the situation is dramatic as 4 out of the 5 ACT available present TF rate higher than 10%. AR is a publi health a threat as AR might spread to Africa.

2. Introduction: Area of Intervention
Population
27 villages
28 Village Malaria Workers
Malaria drug resistance, fuelled by artemisinin resistance, is a reality in the Greater Mekong Subregion. This situation is challenging one because these countries are experiencing high treatment failure rate of the ACTs, the current cornerstone for treatment of Pf.
The Explanation of the background and the imperative need to eliminate Pf in order to avoid spreading of resistance to other parts of the world (Africa)
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

3. Methods: Strategy Season 15-17
Passive case detection (PCD): Early diagnosis and treatment of symptomatic cases. Use of RDT & PCR, by VMW and HC.
Follow up 28 days later after treatment, in PCR, for ruling out treatment failure.
Surveillance of molecular marker of resistance (K13 and pfmdr1)
Reactive case detection (RACD): recruit positives « around » index case: RDT/PCR screening of family and « co-exposed »
Pilot of Pro-active case detection (Pro-ACD) : target asymptomatic parasite reservoir, within at risk populations
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

4. Results DHA-PPQ ASMQ In PCR Treatment Failure # Pf Day 0 tested
Oct 2015-Jan 2016
# Pf Day 0 tested
Result D28 after DHA-PPQ
Total positive
% positivity
Oct 2015-Jan 2016
130 39
30%
D28 after introduction of ASMQ as 1st line treatment (from February 2016 ongoing)
# followed up in Day 28
Total positive
% positivity 50 0%
ASMQ
Treatment Failure
Feb 2016-Mar 2017
Gabriele Rossi, MSF OCB Cambodia:
Pro-Active Case Detection

5. Results: Markers of Artemisinin and Mefloquine Resistance
Out of 194 Pf samples
K13 mutations associated with Artemisinin resistance present in 80% of the analyzable samples.
pfmdr1 amplification more than 1.5 copies (associated with mefloquine resistance)
DHA-PPQ group (Oct 2015-Jan 2016): present in 9%
ASMQ group (Feb 2016-Mar 2017): present in 49%
of the analyzable P falciparum
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

6. Conclusions : Molecular Markers and Drug Resistance Surveillance
K13 mutation is spread and fixed at high level in the district (80% of the Pf are carrying the mutation)
ASMQ is proving to be highly efficacious across 1 year span of ‘drug-resistance surveillance’, based on Day 28 PCR monitoring results
Drug resistance surveillance needs to stay vigilant, in view of the significant increase of the pfmdr1 in the ASMQ treatment group and the possible resurgence of mefloquine resistance
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

7. Introduction: PILOT of Pro-Active Case Detection (Pro-ACD)
Rationale: identifying asymptomatic cases who contribute to form the infectious parasite reservoir
In the present study setting, Voluntary Screening and Treatment (VSAT) is defined as a screening and treatment activity focused on high-risk groups:
spending night in forest and/or
plantation and/or
ricefield and/or
with past history of malaria
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

8. Methods: Pilot in 3 villages in the period Dec 2015- Mar 2016
Additional cases detected (compared to PCD)
Profile of people at risk
Feasibility
Quantitative study
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

9. Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection
Methods: Outline
Check for Positivity Pf
with PCR
Step 4: Day 28
after treatment
Step 1: from
Day -14 to Day 0
HP Sensitization:
- Asymptomatic malaria
- Service promotion for
specific groups
Treatment in DOT
DHA-PPQ
Reactive Case
Detection
Step 2: Day 0
Testing day
(RDT + PCR by finger prick)
and Malariometric Questionnaire
Step 3:
by Day 14
See next slide for explanation of HP activities
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

10. Results: Pf cases detected – Comparison PCD/Pro-ACD
Pf Detection Rate 1.1% (33 Pf cases out of 3075 tested) PCD 17 Pf case Pro-ACD 33 Pf case Ratio PCD/Pro-ACD = 1:2 Pf cases treated within 13 days
Is consistent with the recently published data on numerical parasite DENSITY distribution and is well represented by the image here shown (Iceberg) where the tip is made of patent infections identified by RDT/microscopy and the submersed part by the subpatnt infections. The magnitude/size of the quota intercepted by the low volume PCR is congruent with the ratio 1:2 we obtained, therefore being in favor to the hypothesis that our strategy, by using low volume PCR, identified most of the detectable infections
Which is the magnitude of the intercepted asymptomatic/submicroscopic quota of the infectious reservoir? We do not know. The proportion of Pro-ACD/PCD Pf cases (2:1) is consistent with the predicted Geometrical distribution of Pf densities. But the question remains: were we able to detected all what was detectable ? (in terms of population coverage and diagnostic power of the test)
The numerical distribution of Pf densities (log normal distribution) tells us that up to 75% of sub-microscopic cases can be detected by high volume PCR (22 parasites/ml). The small volume PCR (on 5 microlt blood) can detect up to parasite/ml.
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

11. Results: Coverage & Detection Rate by Age Category
Pf Detection rate higher in the age categories most mobilized
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

12. Results: Risk Profiling
no association with risk of Pf for spending night time in ricefield (P = 0.6)
no association with risk of Pf infection for previous history of malaria (P = 0.5)
association with spending night time in forest (P =0.002; OR 3.4 [ ])
association with spending night time in plantation (P=0.03; OR 2.3 [ ]). Plantations are often embedded in forested areas
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

13. Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection
Conclusions: Pro-ACD
Pro-ACD appeared to confirm the forest goers and Plantation goers, spending night time there, as the group holding a significant risk for Pf infection, regardless of gender
Pro-ACD, under the form of Screening and Treatment is feasible
Pro-ACD found more Pf infections than the PCD, during the same time/place of intervention
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection

14. Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection
Acknowledgments
Cambodia National Malaria Center
Pasteur Institute - Cambodia
Médecins Sans Frontières
MSF Project, Preah Vihear
Medical Department MSF OCB, Brussels
MSF Coordination, Phnom Penh
Gabriele Rossi, MSF OCB Cambodia: Pro-Active Case Detection