**4. Meat inspection changes in monitoring of cysticercosis**

Bovine cysticercosis and porcine cysticercosis are common parasitic infections of mainly skeletal muscles of bovines and swine by larval stages (cysticerci) of the two large tapeworms *T. saginata* (beef tapeworm) and *T. solium* (pork tapeworm). Human taeniosis occurs as a zoonotic consequence of consumption of raw or undercooked meat contaminated by viable larvae of *T. saginata* (*C. bovis*) and *T. solium* (*C. cellulosae*) and further development of their adult forms in human intestines. *T. asiatica* was also described as the new taenia species that parasitize in humans as definitive hosts [6], which geographical distribution is limited to Asia [72]. In addition, unlike *T. saginata* and *T. solium,* this tapeworm infects pigs, cattle, goats, and

#### *Epidemiology of Taeniosis/Cysticercosis in Humans and Animals DOI: http://dx.doi.org/10.5772/intechopen.110727*

certain monkey species as intermediate hosts, in which cysticerci are predominantly located in liver [73]. *T. asiatica* is not considered to cause human cysticercosis [74]. Other *Taenia* spp.*,* such as *T. multiceps,* that parasitize in domestic and wild animals, do not normally invade humans, although cases of coenurosis (infection of the brain, spinal cord, and eyes with *Coenurus cerebralis* as the larval stage of *T. multiceps*) have been reported in humans [75, 76]. Human cysticercosis or neurocysticercosis is another zoonotic form of food-borne infection by *T. solium*, which occurs as a life-threatening illness subsequently to invasion of the central nervous system by *C. cellulosae*. Human cysticercosis is considered as the most dominant helminthic infection of the nervous system and a major global cause of acquired epilepsy [77, 78]. The diseases caused by *T. saginata* and *T. solium* are worldwide reported, with estimates on their occurrence ranging regionally, as well from country to country. As for Bosnia and Herzegovina, the available data are scarce and limited, but cases of human and bovine cysticercosis were reported [79].

Due to the zoonotic potential, bovine, porcine and other forms of animal cysticercosis are notifiable to the World Organization for Animal Health [80]. As for the European Union (EU), monitoring of cysticercosis in the EU Member States (MS) becomes compulsory depending on the epidemiological situation, as regulated by List B of Annex I of the Directive 2003/99/EC [81]. Based on the monitoring data, each MS must evaluate the trends and sources of zoonoses, zoonotic agents, and antimicrobial resistance in their territory and send annual national reports to the European Commission. Each year the national reports from all MS are evaluated and published by European Food Safety Authority (EFSA) as the EU Summary Report on the trends and sources of zoonoses, zoonotic agents, and antimicrobial resistance in the EU. Since 2019, the annual EU Summary Reports on zoonoses, zoonotic agents and foodborne outbreaks have been renamed the "EU One Health Zoonoses Summary Report" (EUOHZ), which is co-authored by EFSA and European Centre for Disease Prevention and Control. The latest published EUOHZ report for 2021 [82] included very scarce data on *Cysticercus* spp. in several animal host species from only eight MS. Frequency of cysticerci detected in bovine carcasses at slaughterhouses was 0.271% (74 positive out of the 27,326 inspected) in Luxembourg, 0.111% in Belgium (857 positive out of the 770,235 inspected), 0.009% in Slovakia (3 positive out of 34,771) and Slovenia (11 positive out of 123,961), 0.005% in Spain (125 out of 2,332,666), while Sweden reported only one positive out of 411,650 inspected cattle carcasses. As for inspected pork, cysticerci were found in 0.001% (7 positive out of 675,234 checked) and in 0.007% (2902 positive out of 41,059,466 inspected) pig carcasses in Slovakia and Spain, respectively. Spain also detected cysticerci in 33 of 111,100 wild boars (0.03%), 17,332 out of 799,767 goats (2.18%), 200,810 out of 7,077,050 sheep (2.84%), and in 110 out of 4544 inspected solipeds (2.42%). Moreover, cysticerci were not detected in 2,200,672 cattle, pig and wild boar carcasses inspected in Finland, in 65,334 cattle, pig, sheep or goat carcasses collected in Malta, or in 7415 mouflons and 118,899 deer inspected in Spain [82].

The existing problem of low reporting data on cysticercosis in EU has been previously recognized and evaluated by the EFSA Panel on Biological Hazard [83] and other scientific report submitted to EFSA [84], where it has been generally assumed that cysticercosis is more frequent in animal and human populations in the EU, with very low sensitivity of slaughterhouse inspection recognized as the main reason for underreporting of cysticercosis.

The major constraint with regard to monitoring of cysticercosis is the lack of a "gold-standard" reference diagnostic test that would solely ensure a high level of

confidence in detecting the disease, particularly in animals with low parasite burdens [85]. Monitoring of cysticercosis is performed by post-mortem meat inspection at the slaughterhouse. Meat inspection by visual inspection, palpation and incision of appropriate organs was originally introduced at the end of nineteenth century by Robert Ostertag [86, 87]. In Bosnia and Herzegovina, post-mortem meat inspection is currently imposed by specific national regulation [88], which is completely harmonized with Regulation (EC) No 854/2004 [89], imposing mandatory visual inspection of all surfaces of each carcass of slaughtered animals by the official veterinarian. In addition, the official veterinarian may require carcasses of bovine animals over 6 months old, and domestic swine over 4 weeks old to be submitted for post-mortem inspection split lengthways into half carcasses down the spinal column. Furthermore, if the inspection so necessitates, the official veterinarian may also require any head or any carcass to be split lengthwise. Also, specific examinations such as palpation and incision of parts of the carcasses (such as predilection locations for cysticerci; tongue, esophagus, diaphragm, internal and external masseters, pericardium and heart), offal and laboratory tests, must be carried out to, among other reasons, detect the presence of a zoonotic disease such as cysticercosis. Also, requirements for systematic visual inspection, palpation, and incisions of carcasses from bovines under and above 6 weeks old, and for domestic swine carcasses are specified as well. In addition to the specified post-mortem meat inspection procedures as the minimum requirements for the examination for cysticercosis in bovine animals over 6 weeks old and swine, the use of specific serological tests is also allowed. In the case of bovines over 6 weeks old, incision of the masseters at post-mortem inspection is not compulsory when a specific serological test is used, as well as when bovine animals over 6 weeks old have been raised on a holding officially certified to be free of cysticercosis. Finally, it is stated that carcasses infected with cysticerci must be declared as unfit for human consumption and condemned. However, when the animal is not generally infected with cysticerci, the uninfected parts may be declared as fit for human consumption after having undergone a cold treatment [90], such as kept at temperatures below −10°C minimally for 2 weeks or at −7°C for at least 3 weeks [91].

Diagnostic sensitivity of the post-mortem visual inspection lower than 30% (or reduced to 1% for very low parasite burden and localized infections) and its questionable specificity triggered by possible misdiagnosis are known, which results in low official reporting and underestimated prevalence of cysticercosis [92]. Also, the effectiveness of visual inspection, incision and palpation in detecting cysticercosispositive carcasses greatly rely on the level of training, experience, and skills of official veterinarians, which makes the post-mortem meat inspection very subjective, timedemanding, and laborious and results in absence of proficiency scheme, ring trials and standardization of the method [86, 92], and in the lack of a proficiency scheme or ring trials. In addition to evident financial costs and losses due to cysticercosis and taeniosis [92], these are the main reasons that alternative diagnostic techniques have been studied to be introduced in meat inspection procedures and improve diagnostics of cysticercosis.

Mostly deficient and unspecific clinical manifestation of the disease in bovines and swine reflects in overall ineffectiveness to screen cysticercosis in animals during the ante-mortem inspection. Bovine cysticercosis does not cause clinically apparent symptoms in infected animals, except for ones with observed multi-organ infestation with *C. bovis*. Gholami et al. [93] described obvious symptoms, such as different degrees of lethargy, dullness, unthriftiness, and reluctance to move in feedlot cattle in Iran, in which post-mortem inspection showed multi-organ infection with the

#### *Epidemiology of Taeniosis/Cysticercosis in Humans and Animals DOI: http://dx.doi.org/10.5772/intechopen.110727*

cysticerci, such as heart, tongue muscle, masticatory muscle, lungs, and liver. The authors reported that the most and least invaded organs were heart (100%) and liver (14.28%), respectively. On the other hand, clinical manifestation of porcine cysticercosis largely depends on localization of *C. cellulosae* in infected pigs, which is primarily in muscle tissue and the brain [94]. Predilection of the cysticerci for the brain of infected pigs may trigger disorders of the central nervous system as dominant clinical manifestations of porcine neurocysticercosis. Trevisan et al. [95] reported that clinical signs of porcine neurocysticercosis included severe seizures with stereotyping walking in circles, chewing motions, foamy salivation, and ear stiffening, accompanied with tonic muscle contractions followed by a generalized rapid loss of muscular function and collapse of the animal. Even though the authors reported a significant positive association between seizures and age of the animals (p < 0.001), they observed the seizures in only two of 16 infected animals, while significant relations between seizures and total number, distribution and localization of cysticerci in the brain were not reported. In addition to seizures, less severe signs of porcine cysticercosis may include excessive salivation, excessive blinking and tearing, and presence of subconjunctival nodule [96], as well as dullness, sluggishness, somnolence, apathy, and loss of consciousness [97, 98].

Unlike irregular and non-pathognomonic neurological manifestations of porcine cysticercosis, localization of *C. cellulosae* in tongue muscular tissue was the rationale for antemortem lingual palpation (tongue inspection) as a rapid and inexpensive tool for pig producers, buyers, and veterinarians to screen cysticercosis in pigs [98]. Dorny et al. [99] reported that lingual palpation was 100% specific in detecting cysticercotic pigs if performed correctly by experienced persons and combined by the visual inspection of the tongue base. However, the authors estimated the overall sensitivity of tongue inspection at only 21%, which confirmed previous observations that the sensitivity of detecting cysticercosis-positive pigs solely by lingual inspection is greatly limited if the tongue is not heavily invaded with the cysts [100]. The sensitivity of tongue inspection fluctuates depending on the infection intensity and the test is suitable only in the areas where porcine cysticercosis is highly endemic [101].

Serological techniques, such as ELISA, have been widely employed to screen cysticercosis in pigs [101–103] and in bovines [104–106], where the estimated values for sensitivity and specificity of the applied tests varied greatly. Chembensofu et al. [103] evaluated the performance of circulating antigen detection (Ag-ELISA) against full carcass dissection as the gold standard method in detecting naturally *T. solium*infected pigs in Zambia. The authors reported the Ag-ELISA specificity and sensitivity in detecting infected carcasses to be 67% and 68%, respectively, and increasing to 90 and 100% for the detection of carcasses with one or more viable cysticerci, and more than 10 viable cysts, respectively. Using a similar approach, Kabulu et al. [101] estimated Ag-ELISA sensitivity and specificity in detecting *T. solium* cysticerci in naturally infected pigs in Tanzania to be 82.7% and 86.3%, respectively, and concluded that the Ag-ELISA test used in the study is more reliable in ruling out *T. solium* cysticercosis in pigs, than in confirming it, since the positive and negative predictive values of the test were 35.2% and 98.2%, respectively. Using an Ag-ELISA test to estimate the prevalence of bovine cysticercosis, Dorny et al. [104] examined 1164 serum samples of cattle slaughtered in Belgium and detected 3.09% cysticercosis-positive serum samples, while the routine post-mortem meat inspection of the same cattle detected the disease only in 0.26% carcasses, which underlines very low sensitivity as the most important disadvantage of the routine meat inspection in detecting cysticercosis. Eichenberger et al. [106] assessed diagnostic values of various ELISA tests

and the EU mandatory antemortem visual meat inspection for detecting *T. saginata* cysticercosis in 793 dairy cows slaughtered in three EU-approved slaughterhouses in Switzerland. In the absence of the "gold-standard" reference diagnostic test, the results of the mandatory meat inspection test and four ELISA tests were further analyzed by use of Bayesian inference. The reported Bayesian estimates of the ELISA tests sensitivity ranged from 14.3% (95% CI: 8.7–21.5) for monoclonal Ab-ELISA to 81.6% (95% CI: 70.1–92.0) for *T. saginata* metacestode excretory/secretory antigen ELISA, while the reported specificity values were between 84.7% (95% CI: 81.6–87.6) for commercial synthesized purified peptide ELISA and 96.3% (95% CI: 93.5–99.0) for *T. saginata* metacestode excretory/secretory antigen ELISA. Sensitivity of the EU routine visual meat inspection was very low, estimated at 15.6% (95% CI: 10.0–23.3), with assumed specificity of 100 [106].

Obviously, the low sensitivity and specificity of the EU mandatory routine visual meat inspection in detecting cysticercosis at slaughterhouses by can be enhanced by combining it with ELISA testing. However, some properties of the ELISA techniques, such as lack of officially registered and commercially available tests for bovine cysticercosis [84] and requirement to be performed by a specialized laboratory [92], make serological techniques unsuitable for routine use to detect cysticercosis in cattle and pigs. In addition, introduction of serological tests for monitoring cysticercosis in animals would greatly increase overall costs related to the disease monitoring. As projected by Jansen et al. [92], employment of an Ag-ELISA test (with estimated sensitivity of 36.37% and specificity of 99.36%) at cattle slaughter would greatly reduce the estimated prevalence of bovine cysticercosis in Belgium from 42.5 to 0.6%. However, such an improvement would generate economic losses for the cattle owners up to 21 million EUR and 10 million EUR for the slaughterhouses just in the first year after implementing the Ag-ELISA, which are enormous increases in financial damages if compared to estimated annual loss of 3.5 million EUR and 200,000 EUR without the test, respectively. Other analytical methods used to for the monitoring and reporting *Cysticercus* in animals and foodstuffs in the EU, such as the parasite taxonomic identification, histopathology, and molecular (DNA) methods were found to be deficient in estimates of their sensitivity and/or specificity, and characterized with lower diagnostic throughput and higher estimated costs when compared to the routine meat inspection and ELISA methods and require specialized diagnostic facilities [84], which has not resulted in routine use of serological methods as an alternative to visual meat inspection [91].

Evidently, meat inspection based on the post-mortem visual inspection, palpation, and incision of carcasses with proven low sensitivity and substantial financial burden need to be advanced toward the risk-based meat safety assurance system in order to provide a better public health protection from meat-borne diseases, as suggested by EFSA [107–109]. To enable MS to perform risk analysis essential for risk categorization of animals and an effective implementation of risk-based meat inspection, EFSA proposed Harmonized Epidemiological Indicators (HEIs) for all meat-producing animal species, including pigs [110] and bovines [111]. The proposed HEIs include, among others, prevalence of hazards in animals or meat at different stages of the food production chain, and other criteria, such as animal hygiene indicators or visible carcass contamination. To be measurable against objective criteria and to achieve an acceptable level, each HEI is defined in terms of respective food production stage, analytical/diagnostic method, and required specimens, if applicable. Such an effort and contribution of EFSA resulted in adoption of the current EU meat inspection legislation [112–115]. The main drive for the change in EU legislation has been to

#### *Epidemiology of Taeniosis/Cysticercosis in Humans and Animals DOI: http://dx.doi.org/10.5772/intechopen.110727*

boost quality improvement and better use of data collected along the integrated food production chain (Food Chain Information—FCI), which are of pivotal importance for establishing reliable HEIs and consequent risk analysis and risk categorization of animal herds. This should enable the shift from the traditional meat inspection approach to the current risk-based meat safety assurance system in which meat of low risk-animals is visual-only inspected (VOI), while meat of high-risk animals is subject to palpation and/or incision [116]. The VOI approach was initiated by the Regulation (EC) No 854/2004 [89] for indoor-raised finisher pigs, while the current Regulation (EU) No 218/2014 [112] allows VOI for all low-risk pigs. As for bovine carcasses, VOI is legalized by the EU Regulation No 2019/627 [115], since the regulation recognizes the actual risks of cysticerci in various cattle categories, which should enable reduction of manual inspection of the carcasses. However, as recognized by Blagojevic et al. [117], a full benefit from legal introduction of VOI approach has not yet been fully achieved, since reduced incisions cause a further decrease in already low sensitivity of traditional meat inspection in detecting bovine cysticercosis, and the additional costs of alternative serological testing hinder its utilization. Challenges and opportunities in the implementation of the new risk-based meat inspection system were recently studied by Antunovic et al. [116]. The authors identified existing trade agreements with third countries, costs of implementation, and inadequate FCI and resistance from meat inspectors as the most frequent obstacles to implementing the new meat inspection systems. In addition, the stakeholders are more confident in the new systems than in the traditional system, while reduced or equal inspection workload compared to the traditional system was observed.

Therefore, further research and expand of means of employing FCI and HEIs are crucial to reach better risk categorization of and enhanced implementation of riskbased meat safety assurance system which should consequently reduce the workload of veterinary inspection, decrease the related costs for the whole meat industry, improve sensitivity of detecting meat-borne hazards and enhance overall public health protection.
