Overcoming challenges in the diagnosis of Schistosoma mansoni infections using POC tests, recombinant protein and monoclonal antibody technology
Authors: Grenfell e Queiroz Rafaella Fortini , Cruz Renata , Pedrosa Maria Luysa , Oliveira Matheus , Jeremias Wander , Assis Jéssica , Coutinho Lucélia , Taboada Diana , Moraes Vanessa , McEwen Lisa , Harn Donald , Coelho Paulo Marcos 
Published: November 2023

Control constraints of Schistosomiasis include the lack of diagnostic methods with high sensitivity. We develop a prospective study in southeast Brazil to standardize new sensitive and rapid diagnostic methods for Schistosoma mansoni infection. Currently, we are investigating 6 endemic areas (>1000 individuals with chronic infection) and 84 travelers infected in a fresh water pool (with acute infection). Sera, urine, feces and saliva samples were used for the standardization/validation of innovative methods, including acute, chronic and post‐treatment patients. Comparisons are performed with eggs in feces by 24 Kato‐Katz slides and 2 analysis of Saline Gardient and clinical symptoms. With our new methods using a selected recombinant protein called CCAr, we were able to detect the disease early as 10 days post‐infection and more than 95% of positive cases from chronic and low endemicity areas were obtained. Plus, POC‐CCA® test was improved with a urine concentration step that turned its sensibility from 6% to 56%. Monoclonal antibody and recombinant protein technologies allowed a superior detection method when comparing it to the conventional methods. In conclusion, data showed 100% of sensitivity of chronic patients and 98% of acute patients.

Support or Funding Information

Fapemig, CNPq, FIOCRUZ, PDTIS (Brazil). Fulbright, NIH, University of Georgia (USA).

Schistosomiasis diagnosis data of the individuals from Estreito de Miralta. Brazil, based on the POC‐CCA results and epg obtained by parasitological methods.

POC‐CCA (1–2 cassettes)
Kato‐Katz
Saline Gradient (1 g of feces)

(2 slides)
(24 slides, 1 g of feces)

49 negative

0 epg
46
42
43

≤10 epg
3
5
4

11–30 epg
0
0
1

31–60 epg
0
2
1

61–60 epg
0
0
0

33 trace

0 epg
24
17
16

≥ <10 epg
9
12
15

11–30 epg
0
1
1

31–60 epg
0
2
1

61–80 epg
0
1
0

2 positive

0 epg
0
0
0

<10 epg
2
1
1

11–30 epg
0
0
1

31–60 epg
0
1
0

61–80 epg
0
0
0

Total

84
84
84
84

doi: 10.1371/journal.pntd.0004778.t001

Schistosomiasis positivity based on POC‐CCA, Kato‐Katz and Saline Gradient among 84 individuals, Brazil.

Prevalence (%)

POC‐CCA

Before lyophilization
2

After lyophilization
32

Kato‐Katz
30

Saline Gradient
30

doi: 10.1371/journal.pntd.0004778.t002

Sensitivity and specificity obtained by POC‐CCA evaluated against a combined reference techniques of 24 Kato‐Katz slides and Saline Gradient (1 g of feces) before and after lyophilization.

Sensitivity (%), 95% CI
Specificity (%), 95% CI

Before lyophilization
6
100

After lyophilization
56
83

doi: 10.1371/journal.pntd.0004778.t003

POC‐CCA performance on schistosomiasis diagnosis before and after lyophilization against parasitological methods.

POC‐CCA (1–2 cassettes)
POC‐CCA after lyophilisation (1–2 cassettes)
Kato‐Katz/Saline Gradient

Negative
49
32
52

Positive
2
27
32

Trace
33
25
‐

Total
84
84
84

doi. 10.1371/journal.pntd.0004778.t004

Descriptive changes on the POC‐CCA results before and after lyophilization process and comparison against parasitological results.

N
Description

Negatives to traces
13
10 patients had no eggs in stool, although 1 presented hookworms eggs. The other 3 patients had 3, 8 and 52 epg of feces

Negatives to positives
11
4 patients with 1, 2, 3 and 55 epg and 7 individuals with no eggs in stool

Traces to positives
15
13 patients showed 1–55 epg while 2 individuals had no eggs in stool, but both presented hookworms eggs

doi: 10.1371/journal.pntd.0004778.t005

Cross reactivity analysis of duplicate POC‐CCA before and after lyophilization of urine samples detected by the combined reference parasitological diagnosis for individuals negative for schistosome eggs.

Results POC‐CCA

Before lyophilization
After lyophilization

Hookworms

Individual 1
Negative
Negative

Individual 2
Negative
Negative

Individual 3
Trace
Trace

Individual 4
Trace
Trace

Individual 5
Trace
Trace

Individual 6
Negative
Trace

Individual 7
Trace
Positive (1+)

Hymenolepis nana

Individual 1
Negative
Negative

Individual 2
Trace
Trace

Individual 3
Trace
Trace

Enterobius vermicularis

Individual 1
Trace
Trace

Individual 2
Trace
Trace

Individual 3
Trace
Trace

Individual 4
Trace
Negative

Ascaris lumbricoides

Individual 1
Trace
Trace

doi: 10.1371/journal.pntd.0004778.t006