Vetera corpora morbo afflicta Actas del XI Congreso Nacional de Paleopatología

Malgosa A, Isidro A, Ibáñez-Gimeno P, Prats-Muñoz G (eds.) (2013) ISBN: 978-84-940187-5-6. p 737-748

ARE THE CRIBRA ORBITALIA INCIDENCES IN 15TH TO 16TH

CENTURY II HAMINA SKELETAL MATERIAL INDICATIVE OF

MALARIA?

Väre T1, Peuraniemi N1, Niinimäki S1,2

1 Laboratory of Archeology, Faculty of Humanities, PL 1000, 90014

University of Oulu

2 Department of Biology, Faculty of Science, PL 3000, 90014

University of Oulu

Correspondencia a: tiina.heikkila@oulu.fi

RESUMEN. El objetivo del estudio es considerar la aparición de cribra orbitalia en relación con la malaria entre los siglos XV y XVI en Ii Hamina. Los cráneos de 102 esqueletos recuperados en la excavación de 2009 en el cementerio de la antigua iglesia de Puerto de Ii fueron examinados para estudiar la cribra orbitalia. Estas lesiones fueron interpretadas como signos de anemia, posiblemente causados por malaria. Las lesiones estaban presentes en la quinta parte de la población, y ambos sexos exhibían una prevalencia similar, sugiriendo que la causa más probable de la anemia era estrés patogénico en lugar de nutricional, por lo que la malaria sería una causa posible. Además, las condiciones ambientales y culturales

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eran favorables para la malaria endémica. Sin embargo, esta es sólo una posible explicación de la aparición de cribra orbitalia.

PALABRAS CLAVE: Cribra orbitalia, malaria, Finlandia, Ii Hamina

ABSTRACT. The aim of this study is to consider the occurrence of cribra orbitalia as an indicator of malaria in Ii Hamina in the 15th to 16th century. The crania of 102 adult skeletons from the 2009 excavation of the old Ii Hamina churchyard were examined for cribra orbitalia. These lesions were interpreted as signs of anemia possibly caused by malaria. The lesions were present in a fifth of the total studied population and their prevalence was similar in both sexes. This suggests that the anemia was not caused by nutritional but by pathogenic stress, which would nominate malaria as one possible causative factor. What is more, the environmental and cultural conditions were favorable for endemic malaria. However, malaria is only one possible explanation for the occurrence of cribra orbitalia in Ii Hamina.

KEYWORDS: Cribra orbitalia, malaria, Finland, Ii Hamina

INTRODUCTION

Our objective was to look at cribra orbitalia (Fig. 1) occurrence in the 15th and 16th century population of Ii Hamina, located on the coast of Northern Osthrobotnia (Fig. 2), as a possible sign of malaria induced anemia. To find support to the hypothesis of malaria as the cause of anemia in this population, we examined the sex-specific distribution of cribra orbitalia lesions. Furthermore, we explored the possibility of endemic malaria considering the environmental conditions and climate in Ii Hamina in the 15th and 16th century. Sporadic cases of malaria could also be explained by individuals infected at endemic areas of malaria who would then have brought the epidemics of the disease to Ii Hamina.

Malaria was common in Finland in the past (Núñez, 2000; Núñez et al., 2003). Unfortunately, in Finland, the archival records prior to the Modern age are scarce. The first recorded incidence of malaria in

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Finland dates to 15th century Naantali (Vuorinen, 2002), which is located several hundred kilometers South from Ii Hamina. However, according to the death register, there were some incidences of malaria during the 16th century in Tornio (Torres and Núñez, 2006), 50 km north from Ii Hamina. The last malaria epidemic in Finland was in the 1940’s (Hernberg, 1947).

In Finland, endemic malaria was caused by Plasmodium vivax (Torres and Núñez, 2006) which is common in temperate areas and leads to a mild form of the disease. P. vivax requires an extrinsic incubation period of approximately two weeks in the temperature of circa 19⁰C before it is infectious to humans. Malaria causes severe anemia as the parasites invade the red cells of the host during their asexual reproduction. After multiplication inside the red blood cells the parasites burst out of the cells destroying them. Malaria parasites are spread exclusively by female mosquitoes of the genus Anopheles, which suck the blood and are therefore able to spread the disease from infected individuals. In Finland, the parasite was probably spread by a species of mosquito belonging to Anopheles maculipennis complex. To breed mosquitoes require wetlands, which are common in Northern Osthrobotnia.

Figure 1. The orbital roofs exhibit cribra orbitalia. Arrows are pointing at the lesions.

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In Scandinavia, in the beginning of the 15th century, there was a favorable climatic period followed by a rapid cooling. The entire Northern hemisphere went through a particularly cold period between the late 16th century and the mid-18th century. (Enbuske, 2010) However, even when general climate was not suitable for endemic malaria, it is still possible that it existed as an indoor-disease (Huldén et al., 2005).

Figure 2. A map of province of Finland of Swedish Kingdom in the middle ages. Routes of trade are marked. According to Tanska (2011).

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Cribra orbitalia is porosity of the orbital roofs. The etiology of the lesions is not clear. Presumably it can be due to anemia which causes venous hypervascularization of the bone marrow. Anemia results from iron deficiency caused by either pathogenic or nutritional stress. For example, iron deficiency due to poor nutrition, blood loss or pathogenic stress can cause anemia. Thus, cribra orbitalia may represent a skeletal manifestation of malaria.

Torres and Núñez (2006) studied the occurrence of cribra orbitalia in the 18th to 19th century Oulu. They examined the cribra orbitalia lesions in the crania of the skeletons from Oulu churchyard dating to the 18th to 19th century. They considered the possibility to interpret the lesions as malaria induced anemia. According to archival evidence malaria was endemic in the neighboring regions of Oulu during that time. Lesions were present in approximately one quarter of the studied individuals. The prevalence was similar for men and women. As women have a pronounced need for nutritional iron due to reproductive purposes, they are more prone to develop anemia as a result from nutritional deficiency of iron than men. As women in the Oulu population did not present higher prevalence of cribra orbitalia it is not likely that the lesions were due to iron deficiency. Therefore, cribra orbitalia could have been a skeletal manifestation of malaria in Oulu. (Torres and Núñez, 2006).

MATERIAL AND METHODS

The material used in this study consisted of skeletons from the 15th to 16th century graveyard of Ii Hamina, excavated in 2009. At least from the 14th century onward, Ii Hamina was a harbor and market place with occasional international visitors (Vahtola, 1989; Tanska, 2011). The hamlet was located in a delta of the river Ii rich with wetlands suited for mosquito breeding grounds.

Altogether, the orbit roofs of 102 adult crania were examined (45 were women, 34 men, and 23 cases of undetermined sex). Most of the material came from a secondary deposit of the skeletal remains (“bone pit”). The skeletal material in the bone pit was fragmentary, poorly preserved, and consisted of disassembled bones. Thus, only the crania and not the associated post-cranial skeletons could be examined for lesions suggesting anemic state of individual.

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RESULTS AND DISCUSSION

Cribra orbitalia lesions were present in about one fifth of the studied individuals (21 out of 102 = 20.59%). Lesions were found in 11 out of 45 women and 9 out of 34 men and in one individual of undetermined sex. Prevalence and sex-specific distribution of cribra

orbitalia lesions in Ii Hamina was fairly similar to that in Oulu (Fig. 3). As the sexes did not differ in the prevalence of cribra orbitalia lesions in this material, these lesions are more likely to represent pathogen induced anemia instead of anemia due to nutritional stress. Furthermore, a study by Walker et al. (2009) suggests that skeletal lesions traditionally interpreted as anemia cannot be due to nutritional iron-deficiency.

During the 15th to 16th century when the Ii Hamina churchyard was in active use there was a climate shift from a warm period to a particularly cold one (Enbuske, 2010). However, according to archival records, there were incidences of malaria in the neighboring areas even during this less favorable climatic period (Torres and Núñez, 2006). It is plausible that malaria remained endemic in the area due to cultural and environmental conditions: people lived close to the mosquito breeding grounds and offered the ideal indoor conditions for the mosquitoes during the extrinsic incubation period of the parasite, thus enabling endemic malaria (Huldén et al., 2005).

However, at least a part of the malaria incidences can be explained by epidemics. The epidemics of malaria could have been brought to Finland by troops engaged in military conflicts. The latest conflict-driven malaria epidemic in Finland was during the Second World War. Malaria also spread northwards during the Finnish Civil War (1918) and the Crimean War (1854-1855) (Forsius, 2001). Similarly military conflicts could have spread malaria in the 15th century, when Novgorod (now Russia) made several attacks to Northern Osthrobotnia. The malaria parasite could also have used local soldiers as vectors when they returned from various wars by the Swedish Crown, such as the Russo-Swedish War in 1495–1497 or the Thirty Years’ War in 1618–1648. In addition, peaceful mobility by merchants, sailors, and other travelers may have occasionally brought an epidemic of malaria to the area. Archival evidence, although from a period after the active use of the Ii Hamina

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churchyard, supports the interpretation of epidemic malaria. According to the death registers of the Ii parish there were only 19 deaths caused by malaria between 1751 and 1850. As the incidences of malaria deaths are so few, it is not likely that they represent an endemic disease. However, as the malaria in Finland was the mild form, it did not always necessarily lead to the death of the infected individual.

Figure 3. The distribution and prevalence of cribra orbitalia in the populations of 18th to 19th century Oulu and 15th to 16th century Ii Hamina.

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The question still remains whether cribra orbitalia is always a manifestation of anemia (Wapler et al., 2004). Vitamin B12 and C deficiencies have also been suggested as possible causes for the lesions (Walker et al., 2009). However, the preliminary pathological analysis of the material does not support that there was a deficiency of these vitamins in the diet in Ii Hamina (Heikkilä, 2011).

CONCLUSIONS

Because of the similar prevalence of cribra orbitalia lesions in both sexes, these lesions are likely to represent anemia not by nutritional but rather by pathological stress, such as malaria. In addition, the prevalence of lesions and distribution between sexes is similar to that in the skeletal material of Oulu where, according to archival records, malaria was endemic (Torres and Núñez, 2006). This suggests that malaria could have been endemic in Ii Hamina, too. Malaria could have occurred in Ii Hamina during the 15th to 16th century either as epidemics, or even as an endemic disease, perhaps due to culture-modified conditions, such as the warmth provided by indoors. However, the presence of the cribra orbitalia lesions does not verify the occurrence of malaria in the population, as there are also other factors affecting their etiology.

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