The Baermann test: Try this parasitology test in your practice
Diagnosis of S. stercoralis infection commonly relies on the detection of larvae from stool samples, tissue biopsies, and other clinical specimens such as bronchoalveolar lavage [12]. For the examination of stool samples, concentration procedures are essential as the number of excreted larvae is usually very low. Commonly used techniques are the Baermann technique and stool culture, for which either plain agar plates or a charcoal copro-culture procedure can be used. Stool cultures have a relatively high sensitivity, since they allow the parasite to enter the free living cycle, but the procedure is cumbersome and time-consuming [13]. On the other hand, serological and molecular techniques have been used as alternative diagnostic approaches for case detection in both endemic and non-endemic settings [1418]. Polymerase Chain Reaction (PCR) based methods showed higher sensitivity than the conventional Baermann (CB) and copro-culture methods [2,4] however, they are expensive to implement as routine diagnostic tools specially in resource limited countries. Suboptimal sensitivity of microscopy-based techniques for the diagnosis of S. stercoralis infections has a negative impact on prevalence measurements and burden of disease estimations [19]. Should you, your institution's press office or the journal office choose to press release your paper, you will automatically be opted out of early publication. We ask that you notify us now if you or your institution is planning to press release the article. All press must be co-ordinated with PLOS. Three grams of fresh stool sample was weighed and placed on cotton-wool gauze (8 layersnon-sterile) of 5x5 cm. A stool pouch was formed and placed on top of 50 mL falcon tube filled with lukewarm water just slightly touching the water surface (Fig 3). The tube was left to stand at room temperature (which is in our case between 25 and 37C) for hours. The supernatant was discarded and the 3 mL sediment was allowed to settle for 30 minutes and then examined under the microscope for the presence of larvae [4]. The detail procedure is given in S2 Text. The diagnosis of internal parasites in companion animals continues to evolve. Efficient methods that allow clinicians to diagnose infections more quickly and implement treatment earlier have helped pets live longer, healthier lives. Because some internal parasites spread zoonotic disease, such advances also help protect owners.
Diagnosis of unicellular parasites is easily accomplished in a clinical setting by examination of a stained blood smear. The best samples to evaluate are those from animals with an acute infection. A more definitive diagnosis or confirmatory testing (such as in the case ofBabesia) may be achieved throughdiagnostic serologyas well as utilization ofdiagnostic laboratory services. Use ofenzyme-linked immunosorbent assay(ELISA) testing methods, such as the SNAP Heartworm Test or SNAP 4Dx Plus Test (), are also useful for in-clinic detection of either antigen or antibody in patients with or without clinical signs of heartworm disease but no evidence of circulating microfilaria detected through manual examination of blood (due to lack of reproducing females at time of testing). The fact we used a single stool sample might, despite an optimal Baermann procedure, still give an underestimation of the actual prevalence of S. stercoralis infection in our study population. Alternative techniques with a higher sensitivity, such as Koga agar plate culture or PCR, could not be used due to the lack of appropriate laboratory facilities. In general, techniques based on the detection of parasite DNA remain a challenge in many regions where strongyloidiasis is endemic. 2.
stercoralis infections reaches significant levels in some tropical and subtropical settings [24], but the global prevalence is believed to be underestimated due to the low sensitivity of the diagnostic tools [59]. Clinical and laboratory diagnostics play a critical role in the understanding of the epidemiology of the disease, guiding the deployment of resources and the implementation and evaluation of intervention strategies. Currently active strategies for the control of STH under the guidance of the World Health Organization (WHO) do not include S. stercoralis as part of the strategy, but the establishment of a new list of targets for STH control programs by the WHO includes an efficient strongyloidiasis control program in school age children (SAC) by 2030 [10]; and this is further supported by the inclusion of ivermectin in WHO`s list of essential drugs for the treatment of STH [11]. Key components of this strategy are diagnostic tools for adequate surveys and the inclusion of drugs active against S. stercoralis, such as ivermectin and moxidectin, in Mass Drug Administration (MDA) programs. In conclusion, our evaluation shows that the modified Baermann with charcoal pre-incubation is a sensitive and affordable diagnostic approach for microscopic detection of S. stercoralis larvae in stool.
Exame baermann - Figure 1. An Angiostrongylus vasorum larva. The tails of larvae of Aelurostrongylus abstrusus and A. vasorum end in an S-shaped kink and have a subterminal spine. The arrow indicates the location of the spine, which is not easily seen in this photograph but can be seen easily by using the fine focus of the microscope.
Lines 103-104: Why did you pick these three methods of running a Baermann technique for S. stercoralis, as I am sure that there are many other modifications used in diagnostic labs? Do you have any data on what proportion of clinical diagnostic labs are using each of the 3 methods you compare? Step 8: Place a few drops on a slide, add a cover slip, and examine the slide under a microscope. The slide can be scanned with the 4X objective lens for the presence of larvae, which can then be examined more closely at a higher power. Since the morphologic features of rapidly moving larvae can be hard to appreciate, place one or more drops of Lugol's iodine solution at the edge of the cover slip. It will diffuse across the slide and kill the larvae in a straight position and also provide some staining to help visualize the larvae. Lugol's iodine is widely available commercially. S. stercoralis is a helminthic parasite affecting an estimated 386 million people worldwide, with the true burden of disease still unknown [1]. The prevalence of S.
- - Discussion: Some of the Baermann modifications lead to a prolonged incubation so that it takes 24 hours or more until results become available. Hence, when these modifications are used, there is not much time difference as compared to charcoal culture or Koga nutrient agar plates. This could be mentioned/discussed.
Traditionally, the funnels were used to hold the water and faeces; more recently, these have been replaced by beakers, which increases larval recovery. As with flotations, the Baermann technique can be quantified. Likewise, the method and choice of flotation solution that may be used to identify parasitic ova, oocysts, or larvae will differ based on specific gravity (SG) of the organism compared to that of the chosen flotation solution. If protozoan infection of the GI tract is suspected, different testing methods may be used to identify and differentiate between oocysts and trophozoites. Ten grams of stool sample were weighed and mixed with two grams of activated charcoal and lukewarm water. The stool sample was transferred to a petri dish with a double layer of tissue paper at the bottom and then covered by single layer of tissue paper at the top to form a small pouch. Incubation was maintained for 1824 hrs at 26C. After incubation, stool samples were suspended for 1 hour in lukewarm water at room temperature (which is in our case between 25 and 37C) and filtered using a conventional Baermann apparatus (a strainer on top of a funnel connected to a rubber hose clamped with a hemostatic clamp) supported by a funnel stand, the single layer tissue paper side of the pouch was facing the strainer, (Fig 2). Afterwards, the lower 10 mL from the water contained in the hose was drained off, centrifuged at 2000 rpm for 5 minutes and 1 mL of the sediment was examined microscopically for the presence of larvae [6]. The detail procedure is given in S1 Text. Our results suggest the superior performance of MBCI. It is relatively easy to implement, simple to perform and comparatively cheaper. The CB is by far the commonly used method in routine diagnostic although this technique significantly underestimates the true burden of the disease and thereby contributing to the exclusion of S. stercoralis from the control strategies. Therefore, MBCI is recommended as a routine microscopy-based diagnostic test for S. stercoralis infection, particularly in settings where molecular procedures are not available.