- Record: found
- Abstract: found
- Article: found
The prevailing infection of Schistosoma japonicum and other zoonotic parasites in bubaline reservoir hosts in the ricefield of lake ecosystem: the case of Lake Mainit, Philippines
research-article
Publication date (Electronic, pub):
27 July 2023
Journal:
Parasitology
Publisher:
Cambridge University Press
Read this article at
There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
Abstract
Bovines are important reservoir hosts of schistosomiasis, placing humans and animals in rice fields areas at risk of infection. This study reported the prevailing infection of zoonotic parasites from bovine feces in the rice fields adjacent to Lake Mainit, Philippines. Formalin Ethyl Acetate Sedimentation was performed on 124 bovine fecal samples from rice fields and documented eggs and cysts from seven parasites: Schistosoma japonicum, Fasciola gigantica, Ascaris sp., Strongyloides sp., Balantidium coli, coccidian oocyst and a hookworm species. Among these parasites, F. gigantica harboured the highest infection with a 100% prevalence rate, followed by hookworms (51.61%), B. coli (30.64%) and S. japonicum (12.09%), respectively. The intensity of infection of S. japonicum eggs per gram (MPEG = 4.19) among bovines is categorized as ‘light.’ Bovine contamination index (BCI) calculations revealed that, on average, infected bovines in rice fields excrete 104 750 S. japonicum eggs daily. However, across all ricefield stations, bovines were heavily infected with fascioliasis with BCI at 162 700 F. gigantica eggs per day. The study reports that apart from the persistent cases of schistosomiasis in the area, bovines in these rice fields are also heavily infected with fascioliasis. The study confirms the critical role of bovines as a reservoir host for continued infection of schistosomiasis, fascioliasis and other diseases in the rice fields of Lake Mainit. Immediate intervention to manage the spread of these diseases in bovines is recommended.
Related collections
Most cited references27
- Record: found
- Abstract: found
- Article: not found
Chapter 2. Fasciola, lymnaeids and human fascioliasis, with a global overview on disease transmission, epidemiology, evolutionary genetics, molecular epidemiology and control.
Fascioliasis, caused by liver fluke species of the genus Fasciola, has always been well recognized because of its high veterinary impact but it has been among the most neglected diseases for decades with regard to human infection. However, the increasing importance of human fascioliasis worldwide has re-launched interest in fascioliasis. From the 1990s, many new concepts have been developed regarding human fascioliasis and these have furnished a new baseline for the human disease that is very different to a simple extrapolation from fascioliasis in livestock. Studies have shown that human fascioliasis presents marked heterogeneity, including different epidemiological situations and transmission patterns in different endemic areas. This heterogeneity, added to the present emergence/re-emergence of the disease both in humans and animals in many regions, confirms a worrying global scenario. The huge negative impact of fascioliasis on human communities demands rapid action. When analyzing how better to define control measures for endemic areas differing at such a level, it would be useful to have genetic markers that could distinguish each type of transmission pattern and epidemiological situation. Accordingly, this chapter covers aspects of aetiology, geographical distribution, epidemiology, transmission and control in order to obtain a solid baseline for the interpretation of future results. The origins and geographical spread of F. hepatica and F. gigantica in both the ruminant pre-domestication times and the livestock post-domestication period are analyzed. Paleontological, archaeological and historical records, as well as genetic data on recent dispersal of livestock species, are taken into account to establish an evolutionary framework for the two fasciolids across all continents. Emphasis is given to the distributional overlap of both species and the roles of transportation, transhumance and trade in the different overlap situations. Areas with only one Fasciola spp. are distinguished from local and zonal overlaps in areas where both fasciolids co-exist. Genetic techniques applied to liver flukes in recent years that are useful to elucidate the genetic characteristics of the two fasciolids are reviewed. The intra-specific and inter-specific variabilities of 'pure'F. hepatica and 'pure'F. gigantica were ascertained by means of complete sequences of ribosomal deoxyribonucleic acid (rDNA) internal transcribed spacer (ITS)-2 and ITS-1 and mitochondrial deoxyribonucleic acid (mtDNA) cox1 and nad1 from areas with only one fasciolid species. Fasciolid sequences of the same markers scattered in the literature are reviewed. The definitive haplotypes established appear to fit the proposed global evolutionary scenario. Problems posed by fasciolid cross-breeding, introgression and hybridization in overlap areas are analyzed. Nuclear rDNA appears to correlate with adult fluke characteristics and fasciolid/lymnaeid specificity, whereas mtDNA does not. However, flukes sometimes appear so intermediate that they cannot be ascribed to either F. hepatica-like or F. gigantica-like forms and snail specificity may be opposite to the one deduced from the adult morphotype. The phenotypic characteristics of adults and eggs of 'pure'F. hepatica and F. gigantica, as well as of intermediate forms in overlap areas, are compared, with emphasis on the definitive host influence on egg size in humans. Knowledge is sufficient to support F. hepatica and F. gigantica as two valid species, which recently diverged by adaptation to different pecoran and lymnaeid hosts in areas with differing environmental characteristics. Their phenotypic differences and ancient pre-domestication origins involve a broad geographical area that largely exceeds the typical, more local scenarios known for sub-species units. Phenomena such as abnormal ploidy and aspermic parthenogenesis in hybrids suggest that their separate evolution in pre-domestication times allowed them to achieve almost total genetic isolation. Recent sequencing results suggest that present assumptions on fasciolid-lymnaeid specificity might be wrong. The crucial role of lymnaeids in fascioliasis transmission, epidemiology and control was the reason for launching a worldwide lymnaeid molecular characterization initiative. This initiative has already furnished useful results on several continents. A standardized methodology for fasciolids and lymnaeids is proposed herein in order that future work is undertaken on a comparable basis. A complete understanding of molecular epidemiology is expected to help greatly in designing global actions and local interventions for control of fascioliasis.
- Record: found
- Abstract: found
- Article: found
Schistosomiasis Research in the Dongting Lake Region and Its Impact on Local and National Treatment and Control in China
Donald McManus, Darren J. Gray, Allen G. Ross … (2011)
Schistosomiasis is a chronic and debilitating parasitic disease that has often been neglected because it is a disease of poverty, affecting poor rural communities in the developing world. This is not the case in the People's Republic of China (PRC), where the disease, caused by Schistosoma japonicum, has long captured the attention of the Chinese authorities who have, over the past 50–60 years, undertaken remarkably successful control programs that have substantially reduced the schistosomiasis disease burden. The Dongting Lake region in Hunan province is one of the major schistosome-endemic areas in the PRC due to its vast marshland habitats for the Oncomelania snail intermediate hosts of S. japonicum. Along with social, demographic, and other environmental factors, the recent completion and closure of the Three Gorges dam will most likely increase the range of these snail habitats, with the potential for re-emergence of schistosomiasis and increased transmission in Hunan and other schistosome-endemic provinces being a particular concern. In this paper, we review the history and the current status of schistosomiasis control in the Dongting Lake region. We explore the epidemiological factors contributing to S. japonicum transmission there, and summarise some of the key research findings from studies undertaken on schistosomiasis in Hunan province over the past 10 years. The impact of this research on current and future approaches for sustainable integrated control of schistosomiasis in this and other endemic areas in the PRC is emphasised.
- Record: found
- Abstract: found
- Article: found
A Novel Procedure for Precise Quantification of Schistosoma japonicum Eggs in Bovine Feces
Bin Xu, Catherine A Gordon, Wei-wei Hu … (2012)
Introduction Schistosoma japonicum, the causative agent of Asian schistosomiasis, is endemic to the People's Republic of China, the Philippines and small pockets of Indonesia [1]–[7]. Unlike African schistosomiasis, mainly caused by S. mansoni and S. haematobium, schistosomiasis japonica is a zoonosis and it is estimated that over 40 mammalian species, comprising 28 genera and 7 orders of wild and domestic animals, can act as reservoirs and harbour S. japonicum infection [8]. The range of mammalian hosts complicates schistosomiasis control efforts and, as well as the public health considerations, the disease adds to the economic burden of communities as S. japonicum infection debilitates domestic livestock that are used for food and as work animals [9], [10]. Bovines, particularly water buffaloes (Bubalus bubalis), have been shown to be major reservoir hosts for schistosomiasis japonica in the lake areas and marshlands of southern the People's Republic of China [11]–[16]. However, their role in schistosome transmission has yet to be fully determined in other endemic areas, notably the Philippines, due partly to inconsistent results obtained with the different methods used for identifying and quantifying S. japonicum eggs in mammalian hosts [17]–[20]. In particular, the presence of bulk debris, including cellulosic fibrous material, in the feces of ruminants often obscures the eggs and impairs their visualization across all current copro-parasitological methods that involve microscopy. Here we describe a new copro-parasitological method, the formalin–ethyl acetate sedimentation-digestion (FEA–SD) technique, which eliminates much of this bulk debris and cellulose material and facilitates much improved microscopic examination of S. japonicum eggs in the feces of bovines and other ruminant hosts. We show the FEA-SD technique is an effective technique for identifying S. japonicum eggs using fecal samples from naturally infected Chinese water buffaloes (Bubalis bubalis) and confirm its reproducibility using parasite-positive samples obtained from carabao, a subspecies (Bubalus bubalis carabanesis), in the Philippines. We show that the FEA-SD method is as efficient as real-time PCR (qPCR) for determining schistosome prevalence in bovines but is less costly to implement. Materials and Methods Ethics Statement The conducts and procedures involving animal experiments were approved by the Animals Ethics Committee of the Queensland Institute of Medical Research (project no. P288). This study was performed in accordance with the recommendations of the Australian code of practice for the care and use of animals for scientific purposes, 2004. The FEA-SD Technique Stool samples were taken intra-rectally from 13 water buffaloes, collected from Jiangxi province, People's Republic of China, shown to be naturally infected with S. japonicum, by the miracidial hatching test (MHT) [21]. The FEA–SD technique was then used on the positive samples to identify S. japonicum eggs, calculating egg recovery rates and bulk debris reduction. Full details of the procedure are as follows: First, bovine stool samples are collected rectally from the animals (approximately 500 g each) by a veterinarian or trained personnel. Each stool sample is homogenized with an applicator stick and 50 g of the stool mixture is taken and mixed to a slurry in a beaker with 300 ml of water. The slurry is then sieved, by pouring the slurry onto a 60 copper mesh (Tyler scale with a pore opening size of 250 µm) and using water to flush the smaller sediment onto a 260 copper mesh (61 µm), held below the 40–60 mesh. Sediment caught on the 260 mesh is washed with water into a conical flask and allowed to sediment naturally for 30 minutes. The excess water is removed, leaving sediment which is poured into a 50 ml tube. Approximately 50 ml of water is added to the conical flask and naturally sedimented for 30 minutes, again removing excess water and pouring sediment into the same 50 ml tube. This is repeated once more, to ensure all sediment is in the 50 ml tube. The tube is topped up to 50 ml with 10% formalin (v/v) and mixed thoroughly by vortexing, before standing at room temperature for 30 minutes to fix the eggs. The Falcon tube is then vortexed and, using a pasteur pipette, 10 ml of the suspension (equivalent to 10 g feces) placed into two 15 ml tubes (5 ml in each; equivalent to 5 g feces) labelled A and B. Ten percent (v/v) formalin solution is added to tubes A and B to take the volume up to 8 ml and the tubes mixed thoroughly by vortexing, after which 4 ml of 100% (v/v) ethyl acetate is added using a glass pipette and vigorously vortexed once more for 30 sec. With the cap of the tubes slightly loosened the tubes are centrifuged at 500 g for 10 minutes, resulting in a four-layer separation (Figure 1). It is important for this step that the tubes are spun at 500 g for stable and efficient debris removal. The ethyl acetate is removed from both tubes by gently rimming the bulk debris layer with a thin applicator stick and decanting the top three layers which are then discarded. Ethyl acetate and 10% (v/v) formalin can be added and spun again if necessary to remove further bulk debris. If the middle layer of bulk debris is very thin the tube should be shaken vigorously and the re-spun for better efficiency. Water is added to the remaining pellet to take the volume up to 5 ml and an equal volume of 10% (w/v) potassium hydroxide (KOH) is added to each tube. The tubes are mixed gently by vortexing to resuspend the pellet and the sample is digested overnight at 37°C. 10.1371/journal.pntd.0001885.g001 Figure 1 Four layer separation of sieved fecal material using the FEA-SD technique. The resulting four layer separation occurs after the addition of 100% ethyl acetate and centrifugation at 500 g. The top layer contains the ethyl acetate, the second layer the bulk debris to be discarded, the third layer comprises 10% (v/v) formalin and the final layer is the remaining sediment containing the eggs. After digestion, the sample is vortexed vigorously and centrifuged at 900 g for 10 minutes. The pellet is washed once with 10–15 ml of water to remove any residual KOH by centrifuging the solution for 10 minutes at 900 g, the supernatant removed and the final pellet is resuspended in 4–6 ml of water (as the samples are now fixed) and stored at 4°C. The sample is now ready for counting the S. japonicum eggs by microscopy. Before counting, the suspension is mixed gently with a pipette and the total volume of tubes A and B counted for each sample, pipetting 200–300 µl onto each slide for microscopy. It is important that this is done as the sensitivity of the procedure increases with the amount of suspension examined. The microscopy was performed blind by two independent microscopists, although this is not essential to the completion of the procedure. Infection intensity (eggs per gram of feces, EPG) is calculated based on the total egg number in 10 g of feces (i.e., the contents of tube A plus tube B). Reduction in Bulk Debris and Egg Recovery In order to determine the effectiveness and reproducibility of the FEA-SD technique in reducing the bulk debris and cellulosic material present in water buffalo feces, stool samples from the 13 Chinese animals were individually processed and the initial and final volumes of debris measured and compared (Table 1). Egg recovery was measured by microscopic examination of each of the normally discarded top 3 layers (Figure 1) for the presence of eggs (Table 2). Eggs in the final sediment were counted as per the protocol described above (Table 3). 10.1371/journal.pntd.0001885.t001 Table 1 Reduction in bulk debris of water buffalo fecal samples from the People's Republic of China by the FEA-SD method. Volume of sediment (ml) *Sample Initial (I) Post FEA-SD (P) I-P (ml) I - P/I % 1A 1.3 0.2 1.1 84.6 1B 1.5 0.2 1.3 86.7 2A 1.6 0.6 1.0 62.5 2B 1.6 0.6 1.0 62.5 3A 1.0 0.4 0.6 60.0 3B 1.0 0.4 0.6 60.0 4A 1.7 0.3 1.4 82.4 4B 1.5 0.2 1.3 86.7 5A 1.8 0.6 1.2 66.7 5B 1.9 0.8 1.1 57.9 6A 2.0 0.8 1.2 60.0 6B 1.7 0.8 0.9 52.9 7A 1.3 0.4 0.9 69.2 7B 1.4 0.4 1.0 71.4 8A 2.5 0.8 1.7 68.0 8B 2.4 1.0 1.4 58.3 9A 1.4 0.3 1.1 78.6 9B 1.5 0.3 1.2 80.0 10A 1.0 0.3 0.7 70.0 10B 1.0 0.2 0.8 80.0 11A 1.0 0.2 0.8 80.0 11B 1.0 0.2 0.8 80.0 12A 1.0 0.3 0.7 70.0 12B 1.0 0.2 0.8 80.0 13A 1.0 0.5 0.5 50.0 13B 1.0 0.6 0.4 40.0 Mean 1.4 0.4 1.0 69.2 SD 12.3 * Equivalent to 5 g feces/sample; n = 26. 10.1371/journal.pntd.0001885.t002 Table 2 Reduction in bulk debris of carabao fecal samples from the Philippines by the FEA-SD method. Sample Initial (I) Post FEA-SD (P) I-P (ml) I - P/I % 1A 1.0 0.2 0.8 80.0 1B 1.2 0.3 0.9 75.0 2A 1.0 0.5 0.5 50.0 2B 1.1 0.5 0.6 54.5 3A 1.3 0.5 0.8 61.5 3B 1.4 0.5 0.9 64.3 4A 1.3 0.3 1.0 76.9 4B 1.4 0.4 1.0 71.4 5A 1.4 0.4 1.0 71.4 5B 1.5 0.4 1.1 73.3 6A 1.3 0.4 0.9 69.2 6B 1.3 0.3 1.0 76.9 7A 1.2 0.6 0.6 50.0 7B 1.2 0.6 0.6 50.0 8A 1.3 0.4 0.9 69.2 8B 1.3 0.3 1.0 76.9 9A 1.1 0.5 0.6 54.5 9B 1.0 0.3 0.7 70.0 10A 1.0 0.3 0.7 70.0 10B 1.1 0.5 0.6 54.5 11A 0.9 0.4 0.5 55.6 11B 1.0 0.5 0.5 50.0 12A 1.0 0.5 0.5 50.0 12B 1.2 0.4 0.8 66.7 13A 1.5 0.6 0.9 60.0 13B 1.6 0.5 1.1 68.8 14A 1.6 0.9 0.7 43.8 14B 1.6 0.9 0.7 43.8 15A 1.2 0.5 0.7 58.3 15B 1.2 0.6 0.6 50.0 16A 0.8 0.3 0.5 62.5 16B 0.7 0.3 0.4 57.1 17A 1.0 0.5 0.5 50.0 17B 1.0 0.5 0.5 50.0 18A 1.0 0.4 0.6 60.0 18B 1.1 0.4 0.7 63.6 19A 0.9 0.5 0.4 44.4 19B 0.9 0.5 0.4 44.4 20A 1.0 0.4 0.6 60.0 20B 1.0 0.4 0.6 60.0 22A 1.1 0.3 0.8 72.7 22B 1.0 0.3 0.7 70.0 23A 1.0 0.3 0.7 70.0 23B 1.2 0.4 0.8 66.7 24A 1.3 0.4 0.9 69.2 24B 1.4 0.5 0.9 64.3 25A 1.0 0.4 0.6 60.0 25B 1.1 0.3 0.8 72.7 Mean 1.2 0.4 0.7 61.8 SD 10.2 10.1371/journal.pntd.0001885.t003 Table 3 Reproducibility in recovery of S. japonicum eggs in buffalo fecal samples from the People's Republic of China using the FEA-SD technique. Number of eggs Sample/Tube Water supernatant (W) Bulk debris (BD)*** W+BD Bottom sediment Total Egg recovery rate (%)**** *Sample 1 **Tube A1 0 1 1 50 51 98.0 Tube B1 1 2 3 66 69 95.7 Sample 2 Tube A2 0 2 2 46 48 95.8 Tube B2 0 5 5 66 71 93.0 Sample 3 Tube A3 0 2 2 45 47 95.7 Tube B3 0 5 5 64 69 92.8 Mean 95.2 SD 2.0 * Equivalent to 10 g feces. ** Equivalent to 5 g feces. *** BD: Sediment in the bulk debris layer (Figure 1) removed during the FEA-SD procedure. **** Egg recovery rate (%) = number of eggs in the bottom sediment/total number of eggs in the sample ×100. Application and Reproducibility of the FEA-SD Method Using Fecal Samples Collected from Philippines Carabao Twenty-five carabao fecal samples were collected intra-rectally from S. japonicum-endemic barangays (villages) from Western Samar province, the Philippines. These were subjected to the FEA-SD procedure applied earlier in China with the debris reduction measured (Table 2) and the final egg counts from Tubes A and B for each of the 25 samples determined (Table 4). Full details of the sample collection and methods used can be found in Gordon et al. 2012 [22]. 10.1371/journal.pntd.0001885.t004 Table 4 Recovery of S. japonicum eggs in carabao fecal samples from the Philippines using the FEA-SD technique. Sample/Tube Eggs recovered* Total Sample/Tube Eggs recovered* Total Sample 1 Sample 14 Tube A1 3 Tube A14 1 Tube B1 6 9 Tube B14 2 3 Sample 2 Sample 15 Tube A2 2 Tube A15 0 Tube B2 1 3 Tube B15 0 0 Sample 3 Sample 16 Tube A3 0 Tube A16 0 Tube B3 1 1 Tube B16 2 2 Sample 4 Sample 17 Tube A4 0 Tube A17 5 Tube B4 8 8 Tube B17 0 5 Sample 5 Sample 18 Tube A5 9 Tube A18 5 Tube B5 11 20 Tube B18 7 12 Sample 6 Sample 19 Tube A6 1 Tube A19 2 Tube B6 1 2 Tube B19 2 4 Sample 7 Sample 20 Tube A7 2 Tube A20 0 Tube B7 1 3 Tube B20 1 1 Sample 8 Sample 21 Tube A8 0 Tube A21 5 Tube B8 2 2 Tube B21 6 11 Sample 9 Sample 22 Tube A9 0 Tube A22 1 Tube B9 0 0 Tube B22 3 4 Sample 10 Sample 23 Tube A10 2 Tube A23 3 Tube B10 7 9 Tube B23 7 10 Sample 11 Sample 24 Tube A11 0 Tube A24 2 Tube B11 4 4 Tube B24 6 8 Sample 12 Sample 25 Tube A12 2 Tube A25 0 Tube B12 0 2 Tube B25 3 3 Sample 13 Tube A13 0 Tube B13 4 4 Comparison of the FEA-SD Method with Other Fecal Examination Techniques The FEA-SD was compared directly with other fecal examination techniques including Kato-Katz (KK), the MHT, a validated qPCR assay and conventional PCR on 44 fecal samples collected during the same survey in Western Samar province referred to above. Full details of the sample collection and methods used can be found in Gordon et al. 2012 [22]. Results The FEA-SD technique removed an average of 61.5% — 69.2% of the bulk cellulose debris from the Philippine and Chinese, respectively, bovine stool samples prior to microscopic examination (Tables 1, 2). Any remaining debris was rendered transparent by the potassium hydroxide digestion step, so that eggs were readily observed compared with previous copro-parasitological techniques employing sieving only (Figure 2). Few eggs were present in the discarded bulk debris and supernatant, with an average of 95.2% of the total eggs recovered found in the final sedimented pellet (Table 3). Prevalence determined by the FEA-SD in the study undertaken on water buffaloes in the Philippines showed the FEA-SD (93.2%, 95% CI 85.4–100) had a similar sensitivity (90.9%, 95% CI 82.1–99.8) as the qPCR assay. By contrast the conventional PCR (31.8%, 95% CI 17.5–46.1), KK (25%, 95% CI 11.7–38.3) and MHT (19.1%, 95% CI 0.9–41.2) (Figure 3) gave much lower prevalence [21]. 10.1371/journal.pntd.0001885.g002 Figure 2 Visualization of S. japonicum eggs (circled) in water buffalo feces. Top panel; egg visualization after sieving of feces only. Lower panel; egg visualization after feces are subjected to the FEA-SD technique. 10.1371/journal.pntd.0001885.g003 Figure 3 The FEA-SD method compared with other diagnostic techniques (Modified from Gordon et al. [22]). FEA-SD, formalin–ethyl acetate sedimentation-digestion technique; qPCR, quantitative PCR; PCR, conventional PCR; KK, Kato Katz method; MHT, miracidial hatching test. 95% confidence intervals are shown. Discussion The amount of faeces excreted in one defecation by a large animal such as a water buffalo can exceed 45 kg so it is important to determine the minimal amount of feces that can provide optimal and consistent results using the FEA-SD technique. It was found that a sample of 10 g of feces (divided into tubes A and B) was critical for accurate quantification; as a comparison, 5 g of feces resulted in very inconsistent egg counts between tubes A and B. The direct microscopic identification of schistosome eggs is the ‘gold’ standard for the diagnosis of zoonotic schistosomiasis in both animals and humans. The current microscopic methods of choice for the identification of S. japonicum eggs in bovines and other ruminants are, however, limited in terms of sensitivity and include, among other procedures, the MHT followed by a sedimentation filtration method, and the Danish Bilharziasis Laboratory (DBL) technique [23] (Table 5). More recently developed techniques include FLOTAC and the use of magnetic beads (Helmintex test) which have been shown to detect helminth eggs in low intensity infections [24]–[29]. Immunological techniques have also been applied to diagnostics however cross reactivity and identification of past infections, rather than current infections, have been issues. A recent study looking at Thioredoxin Peroxidase-1 in an ELISA system for identification of S. japonicum in bovines has shown promising results and no cross reaction with a closely related species [30]. 10.1371/journal.pntd.0001885.t005 Table 5 Published studies of diagnostic procedures for identification of S. japonicum eggs in bovine feces. Location of study [Reference] Year Diagnostic Bovine Prevalence (%) Intensity (EPG) Poyang Lake, P. R. China [33] 2002 MHT+filtration Cattle & water buffalo 14 42 Hubei, P. R. China [36] 1994 MHT+filtration Water buffalo 35.7 0.4* Anhui, P. R. China [37] 2010 MHT+filtration Water buffalo 10.5 3.4 Cattle 46.5 2.3 Sichuan, P. R. China [38] 2006 MHT+filtration Cattle 22.3 - Hunan and Jiangxi, P. R. China [12] 2007 MHT+filtration Cattle 21.7 0.5–7.2* Water buffalo 14.9 0.5–7.2* Dongting Lake, P. R. China [39] 2007 MHT Cattle 6.1 - Water buffalo 9.5 - Leyte, the Philippines [17] 2010 MHT Water buffalo 0 - KK 3.7 - DBL Technique 3.7 - qPCR 51.5 2.1* Samar, the Philippines [22] 2012 MHT Water buffalo 19.1 - KK 25 4.7* FEA-SD 93.2 1.2* qPCR 90.9 6.1* PCR 31.3 - Samar and Sorsogon, the Philippines [19] 2005 DBL technique Water buffalo 6.3 - Samar, the Philippines [40] 2007 DBL technique Water buffalo 2.1 - Mindoro, the Philippines [41] 1999 Formalin detergent technique Water buffalo 0 - Leyte, the Philippines [42] 1981 Merthiolate iodine-formaldehyde concentration (MIFC) technique Cattle 0 - Water buffalo 0.38 - Leyte, the Philippines [43] 1958 Glycerol sedimentation with egg hatching and sedimentation counting of eggs remaining Water buffalo 1.5 - Cattle 3.82 - Leyte, the Philippines [44] 1982 MIFC and Circumoval Precipitin Test (COPT) Cattle 1 (MIFC) - Cattle 0 (COPT) - Water buffalo 9 (MIFC) - Water buffalo 1 (COPT) - Cagayan, The Philippines [30] 2012 COPT ELISA Water buffalo 34 (COPT) - 36 (ELISA) - * Geometric mean eggs per gram (EPG). All other values are arithmetic mean EPG. MHT, miracidial hatching test; DBL, Danish Bilharziasis Laboratory method; KK, Kato-Katz technique; qPCR, quantitative real time PCR. The MHT has been used extensively in the People's Republic of China for the identification of S. japonicum in bovine feces [11]. The MHT – a qualitative diagnostic test – involves the concentration of ova from saline using fresh feces through a nylon tissue bag and suspension in distilled water. Miracidia are visualized macroscopically and their presence is diagnostic of infection; three hatches (50 g feces per hatch) are routinely carried out. The MHT is preferred to the Kato Katz technique (KK) (recommended for diagnosis of intestinal schistosomiasis in humans) [26], [31], [32] and the other microscopic methods, due to the large volume of feces produced by bovines, and the fact that, as discussed, bovine feces contain considerable amounts of cellulosic material. This obscures the microscopic visualization of schistosome eggs making slide reading difficult and hindering diagnosis. A drawback of the MHT is that it has fairly rigid requirements for suitable pH, temperature and water quality, which cannot always be met under field conditions. Furthermore, it does not, on its own, provide infection intensity information and, like the KK, its sensitivity decreases as infection intensity decreases. In order to obtain intensity of infection estimates, additional microscopic visualization of eggs is performed on MHT-positive samples following a filtration sedimentation procedure whereby 50 g of feces are passed through 30 (595 µm) and 150 (90–105 µm) sieves and the flow through suspended in a nylon bag to capture the sediment which is then resuspended and the eggs present counted [33]. This is similar to the DBL technique [21] and the same problem of the presence of cellulosic material is common to both procedures. The differences in sensitivity of these different techniques for examining ruminant feces for the presence of S. japonicum eggs makes it difficult to compare historical data for prevalence and incidence and infection intensity and to evaluate the involvement of potential reservoir hosts, particularly bovines in schistosomiasis transmission. Table 5 reviews the published studies of diagnostic procedures for the identification of S. japonicum in bovines and the inconsistent data obtained for prevalence and intensity. Telling examples are our recent pilot survey of S. japonicum infection in carabao from Western Samar [22] and the results of another recently published (2010) study on carabao from Leyte, the Philippines, which showed very low S. japonicum prevalence by KK (3.7%), the DBL technique (3.7%) and the MHT (0%) but a high prevalence (51.5%) using qPCR on the same fecal samples [17]. These two studies clearly highlighted the requirement for a more accurate microscopic technique, exemplified by the FEA-SD method, if only to validate diagnosis by qPCR. The FEA-SD technique, including sieving, sedimentation, centrifugation and digestion, takes approximately 1.5 hours to complete. The length of time taken for subsequent slide reading depends on the skill and experience of the technicians involved, but two well trained and experienced microscopists are able to read one sample in 20 minutes. This procedure is relatively straight forward and only requires a centrifuge. Bovine feces comprise a large mass containing primarily cellulosic fibres and a direct count is the only way to get infection intensity but the debris obscure eggs to a large extent and the FEA-SD is the only currently available technique which clears a large proportion of the debris and renders remaining debris transparent, thereby increasing egg visualisation (Figure 2). Based on cost of reagents only, the FEA-SD technique is far less expensive ($US0.65) to perform than qPCR ($US9.2) although both approaches provide a very similar level of diagnostic accuracy [22]. We are currently using the FEA-SD method to determine the prevalence and intensity of S. japonicum in large animal cohorts as part of extensive epidemiological and surveillance studies we are undertaking in both the People's Republic of China and the Philippines. In summary, the FEA-SD method is an improved tool that can be used to visualize schistosome eggs and to determine the prevalence and intensity of infection of S. japonicum in bovines. The increased visibility of eggs in the final sediment (Figure 2) compared with the DBL, MHT (+filtration) and KK techniques, makes the FEA-SD an important new technique applicable for epidemiological studies where bovines and other ruminants, such as goats, are potentially important reservoir hosts for S. japonicum [11]–[13], [34], [35]. In addition to S. japonicum the FEA-SD method can also be used to identify and quantify eggs of other helminths, such as Fasciola sp. in naturally infected animals. The FEA-SD also has the benefit of costing less than qPCR, which increases its potential as a surveillance tool for evaluating control programs, including in areas where control has led to the suspected elimination of schistosomiasis japonica.
Author and article information
Journal
Journal ID (nlm-ta): Parasitology
Journal ID (iso-abbrev): Parasitology
Journal ID (publisher-id): PAR
Title:
Parasitology
Publisher:
Cambridge University Press
(Cambridge, UK
)
ISSN
(Print):
0031-1820
ISSN
(Electronic):
1469-8161
Publication date
(Print, pub):
August
2023
Publication date
(Electronic, pub):
27
July
2023
Volume: 150
Issue: 9
Pages: 786-791
Affiliations
Author notes
Corresponding author: Leonardo A. Estaño; Email:
leonardo.estano@
123456g.msuiit.edu.ph
Author information
Leonardo A. Estaño
https://orcid.org/0000-0002-9300-6086
Article
Publisher Item ID: S0031182023000537DOI: 10.1017/S0031182023000537
PMC ID: 10478044
PubMed ID: 37496395
SO-VID: 55fc1d53-b79e-42e5-b1ee-9e72f137f945
Copyright © © The Author(s) 2023
License:
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
History
Date
received
: 22
March
2023
Date
revision received
: 14
May
2023
Date
accepted
: 20
May
2023
Page count
Figures: 1,
Tables: 5,
References: 29,
Pages: 6
Funding
Funded by:
Philippine Council for Health Research and Development, doi http://dx.doi.org/10.13039/501100011096;
Categories
Subject:
Research Article
ScienceOpen disciplines: Parasitology