Detection of pig farms with Ornithodoros erraticus by pig serology. Elimination of non-specific reactions by carbohydrate epitopes of salivary antigens

Ornithodoros erraticus is the European vector of African Swine Fever. It is therefore essential to know on which pig farms the tick is present in order to prevent contact with swine. Currently, studies are being made to ascertain this through the detection of anti-O. erraticus antibodies in the sera of swine, using three extracts from the salivary glands of the parasite (SGE): a complete extract (SGE-1), a soluble antigens extract (SGE-2), and a tissue antigens extract (SGE-3). The results of the present work show that SGE-2 gives the best differentiation between swine bitten by O. erraticus and unbitten swine in the enzyme-linked immunosorbent assay (ELISA). Using this extract, an optical density (OD) five-fold higher than the basal OD indicates that the pigs carry anti-O. erraticus antibodies. A serological study carried out in Salamanca with 8083 sera from 1756 pig farms revealed the presence of the parasite on 135 farms. However, during this study we noticed that some sera of unbitten animals gave false-positive reactions. Western blot analysis of SGE-2 of these false-positive sera demonstrated the same bands (except for two) as the real anti-O. erraticus sera. We observed, in ELISA and Western blot analysis, that such false-positive sera only recognised carbohydrate epitopes on SGE-2. This reactivity disappeared on deglycosylated SGE-2 (SGE-2-P). Therefore, SGE-2-P is the antigen that confers the greatest specificity to serology. In this study it was also observed that the low levels of anti-O. erraticus antibodies found in some cases may be because the swine were bitten some months previously on a different farm or that the current farm harboured only a few specimens of O. erraticus, so pig-tick contact is unlikely and hence the pigs either only develop a primary response or the time between contacts is very long and the levels of antibodies fall. Since pigs could be bitten on a different farm, the presence of low levels of anti-O. erraticus antibodies in pig sera do not necessarily indicate the presence of the tick on the farm where sampling was carried out.

Parasites of the skin and hair

Because scratching is nature's treatment for ectoparasites, they should be considered in the differential diagnosis of any pruritic rash. Usually, the diagnosis is not difficult to make if the clinician suspects an ectoparasitic cause and is familiar with the symptoms and signs of these disorders. The diagnosis is confirmed using a few instruments and basic office supplies. The clinician must treat not only the individual patient but must also consider the source of the infection because others may require treatment. Family and community education about removal of the parasites from the patient's environment is one of the clinician's responsibilities.

[Ixodes ricinus bites]

Ticks (Ixodes ricinus) are found all over the world, with special preference of a few epidemic areas. They do not only invade their hosts one by one, but often in large groups.

Seed ticks

Seed ticks, the first-stage larvae of hard ticks, are not always recognized. They are tiny (0.6 mm) and have six legs, rather than the eight legs found on nymphal and adult ticks. Seed ticks may transmit Rocky Mountain spotted fever, tularemia, babesiosis and Lyme disease. Pediculocides are effective in removing the larvae.

[Tick-borne meningoradiculitis--a form of spirochetosis]

Three pediatric cases of tick-borne meningoradiculitis are presented. This disease is characterized by a distinct sequence of symptoms: erythema chronicum migrans, localized pain, and eventually radicular asymmetric neurologic involvement (in particular facial palsy) associated with findings of aseptic meningitis. On the basis of specific serologic data in these three patients, it is suggested that the etiology of tick-borne meningoradiculitis is also spirochetal , as recently shown for the tick-associated Lyme disease. Analogue positive spirochetal antibody titers were found in additional patients with erythema chronicum migrans and in a child with B afverstedt cutaneous lymphadenosis (see addendum). 20% of tick specimens collected in the area of Lucerne (Ixodes ricinus) were infected by these spirochetes.

Common ectoparasites

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Antibody- and cell-mediated immune resistance by guinea pigs to adult Amblyomma americanum ticks

Naive and actively and passively sensitized guinea pigs were infested with adult Amblyomma americanum ticks. Naive hosts allowed for 75-81% tick yield, 518-581 mg mean tick weight and an average tick feeding period of 12-13 days. Actively sensitized and challenged hosts, however, allowed only 47% tick yield (38.9% rejection), replete individuals were significantly reduced in weight (66.1% weight decrease) and required slightly longer time to feed (14 days). Passively sensitized hosts were given either serum or peritoneal exudate cells (PEC) harvested from actively sensitized and challenged guinea pigs which had expressed resistance. Recipients of immune serum allowed 56% tick yield (27.3% rejection), replete individuals had a mean weight of 376 mg (35.3% reduction) and required an average feeding period of 15 days. However, recipients of immune PEC were conferred with stronger protection allowing only 50% tick yield (35.1% rejection) with a mean tick weight of 413 mg (28.9% reduction) and females required an average feeding period of 15 days to become replete. Cutaneous cellular responses to tick feeding in naive animals were dominated by neutrophils in both female and male attachment sites (62-64%), with the cellular response (lesion) in female sites being 10 times that of male sites. In actively sensitized and challenged (resistant) hosts, cutaneous cellular responses to both females and males were dominated by basophils (53-59%), and lesion size was nearly 20 times greater than in primary feedings, indicating heightened sensitivity to tick bite.

Factors affecting the detection of infestations of Boophilus microplus in tick control programs

Factors affecting the probability of detecting infestations of Boophilus microplus when herds of cattle are examined were studied. The probability of detecting a tick depends on the number of infested cattle in the herd, the probability of ticks being present on the areas of the beast examined, the efficiency of the examination and the proportion of the herd examined. A mathematical expression relating these factors was derived, and a range of values calculated to demonstrate the relative importance of each factor. It was evident that the efficiency of the examination should be kept better than 75%, and that it is necessary to employ a high sampling rate, preferably 100% of the herd. The probabilities of ticks being present on 6 predilection sites and 4 combinations of sites of an infested animal were determined experimentally. The tail butt, esutcheon, belly, dewlap and to a lesser degree neck and ear were all very suitable sites on which to find cattle ticks. A combination of tail butt, escutcheon and neck produced probabilities (0.58 and above) considered adequate to form the basis of an examination system. Examination systems used in New South Wales, Queensland, Argentina and at the United States-Mexico border are described. As a result of this study a new standardised system has been adopted by the Board of Tick Control for use by all New South Wales inspectors.