## 3 From the Field to the Lab  
The sampling strategy in the field is simple and samples are taken by the archaeologist or the anthropologist during the excavation. All structures and areas where organic remains (particularly fecal matter and intestinal residues) tend to accumulate can be targeted. These structures can be divided into two categories: 1/Human and other animal skeletons and mummies. 2/Accumulation structures, i.e., lattrines, pits, sewers, or soils with accumulated organic matter. For skeleton sampling, the main samples should be taken around the pelvic region of the body, precisely just under the hip bones, the last vertebrae, and the femurs. Control samples are taken under the skull and/or the feet (Figure 1A). For accumulation structures such as lattrines or pits, the sampling strategy depends on the type of filling. In case of a homogenous filling, samples should be taken regularly from the top to the bottom with a minimum of three samples. For fillings showing SU, samples should be taken from each SU (Figure 1B). In these two cases, control samples should be taken in contemporary layers outside the structure. Sediment core sampling is also possible. These approaches are particularly suitable for questions relating to variations in the function of the structure throughout time. In the case of soil sampling, for example in occupation layers, a horizontal systematic sampling strategy can be chosen (one sample per square meter for example), or a sampling strategy covering a large part of the layer in the excavated zone, as shown in Figure 1C. This sampling strategy is obviously recommended when preservation conditions are favorable to a spatial approach and it is optimal for a synchronic diagnosis of the parasitic burden. Each sample should consist of roughly 20-100 g of sediment so that several tests can be made. Finally, for coprolite finds, possibly associated with skeletons or mixed with the fillings of accumulation structures (latrines or soils), sampling is recommended over 2-3 cm, in addition to the sediment situated just under the coprolite.  
For all types of analysis (microscopy, immunology, aDNA), clean tools and containers have to be used for each sample to avoid contamination, false-positive signals, and loss of material. In this aim, double containers are recommended. Moreover, it is preferable to collect samples as soon as possible to avoid modern contamination (by wandering animals at night, for example). Samples should be stored in dry and dark conditions, and if possible refrigerated, and no operations (e.g., sieving, sunlight drying, or chemical exposure) should be conducted prior to paleoparasitological analysis. Samples are then processed according to a specific protocol allowing for the extraction of the sought-after ancient parasitic markers. For gastrointestinal worm eggs, modern coprology methods are often of limited effectiveness due to the physicochemical changes related to taphonomic phenomena. Units specialized in the research of ancient parasites mostly use tripartite extraction techniques (rehydration, homogenization, and filtration/micro-screening) with specific adaptations [37; 38; 39]. Observations and counts are then carried out under the microscope. The study of biomolecules often requires the establishment of collaborations with specialized laboratories or takes place in specialized and adapted rooms. Examples of paleogenetic analyses are presented below.  
Figure 1: Various sampling strategies depending on various archaeological context: (**A**) sampling on skeletons; (**B**) sampling in hollowed structures as latrines or pits; (**C**) sampling in occupation layers (example of Zurich Parkhaus Opera, Switzerland).