**4. The Importance of Butantan Institute in Antilonomic Serum Treatment**

The hemostatic disturbances observed in the envenoming by *L. obliqua* caterpillars result in a consumption coagulopathy (resembling a DIC) and secondary fibrinolysis, which can lead to the hemorrhagic syndrome [8,19,28,36]. Treatments with antifibrinolytic drugs such as aprotinin and ε-aminocaproic acid associated with whole blood, freshfrozen plasma, or cryoprecipitates were initially used to treat patients; however, rather than reverting symptoms, the treatment exacerbated them [3,6,7,14,16,28]. In 1996, Da Silva and collaborators [3] developed the ALS from horses immunized with four doses of *Lonomia obliqua* bristle extract (LOCBE), producing antibodies capable of neutralizing the components responsible for typical noncoagulated blood induced by contact with *Lonomia* caterpillars in rats. The developed antivenom is composed of specific immunoglobulin F(ab')2 fragments purified from horse plasma [4].

Clinical studies showed that hemostasis alteration in this kind of accident could be severe within the first 6 h, with intense fibrinogen reduction [8,19]. The patients with the occurrence of abnormal coagulation in screening tests, such as thrombin time (TT), fibrinogen (Fg) concentration, and whole-blood clotting time (WBCT) or hemorrhage manifestations must be hospitalized to receive treatment with ALS according to the Guidelines of the Ministry of Health of Brazil. After the introduction of ALS therapy, the number of deaths resulting from lonomism was reduced. Currently, ALS is the only specific therapy used to treat victims of *L. obliqua* envenomation and is widely distributed by the Ministry of Health in Brazil. Fibrinolytic agents are not recommended for treatment as the venom mainly contains procoagulant agents [7,8,27,28,36]. The correction of anemia due to blood loss should be instituted through the administration of packed red blood cells [27]. Whole blood or fresh plasma are contraindicated, since intravascular coagulation can be accentuated. The recommended doses of ALS in the treatment, according to severity, are shown in Table 1.


**Table 1.** Classification of the severity of accidents by *L. obliqua* and therapeutic guidance according to the Brazilian Ministry of Health [27,28].

#### **5. Blood Coagulation Alterations**

One of the main clinical manifestations of *Lonomia* envenoming is the consumption of coagulopathy due to depletion of coagulation factors, as well as a secondary activation of fibrinolysis accompanied by bleeding into the skin or mucosa, as described by Zannin and collaborators [8]. Hemostatic changes were observed in patients who have had contact with larvae of 5 cm or more corresponding to the last larval instars shortly before entering the pupal stage [36].

The hemorrhagic syndrome developed by patients is a consequence of a type of DIC [8,28]. DIC is defined as a pathological syndrome that results in thrombin formation, activation and consumption of some coagulation factors, and fibrin clot formation [37].

According to Zannin and collaborators [8], the global clotting times (thrombin time— TT, prothrombin time—PT, and activated partial thromboplastin time—aPTT) were prolonged in most cases and were related to an intense reduction in plasma fibrinogen. The levels of von Willebrand factor (vWF), Protein S, tissue plasminogen activator (tPA), and urokinase were not altered, while the levels of factors V and VIII and prekallikrein (PK) were reduced, and this reduction can be attributed to consumption suffered in the activation of coagulation. Factors XII, II, and X levels were unchanged. These results indicate that the consumption coagulopathy developed in this envenomation is different from that observed in DIC associated with other clinical conditions, in which these factors are usually reduced [37–39]. On the other hand, activation of the contact phase of coagulation is unlikely since factor XII levels were normal, although PK levels were shown to be reduced. Zannin and collaborators [8] suggested that PK could be activated by some component of the venom. A subtle reduction in factor XIII was observed in patients envenomed by *L. obliqua*, different from *L. achelous* envenoming where a drastic reduction in this factor is observed, attributed to a factor that degrades FXIII, present in the hemolymph of *L. achelous*, which was called "Lonomin V" [40]. The generation of fragments 1 and 2 of prothrombin (F1+2) and the thrombin/antithrombin complex (TAT) was also observed, like DIC. Although the generation of F1+2 and TAT confirms the formation of thrombin, the number of platelets was not altered in the blood of the patients. Regarding coagulation inhibitors, there was a marked reduction in the levels of Protein C, and there was no significant consumption of antithrombin (AT), as observed in other cases of DIC. Moreover, the formation of thrombin and the TAT complex was observed mainly in patients with severe coagulopathy. These results suggest that AT activity does not depend on coagulation activation. Thrombocytopenia in patients is rare, and its absence can be explained by the high generation of fibrin degradation products (PDFn) suggested by the extremely high levels of D-dimers (DD) [8,19,41,42]. In patients with high levels of DD, a reduction in proteins involved in the fibrinolytic system such as plasminogen, plasminogen activator inhibitor (PAI), and α2-antiplasmin (α2-AP) was observed. In blood coagulation, DD is generated by the action of plasmin on crosslinked fibrin, while the action of plasmin on fibrinogen is observed by the generation of another class of degradation products (PDFg) [43]. Thus, the high increase in DD in patients envenomed by *L. obliqua* suggests that the observed fibrinolysis is an event secondary to the formation of intravascular fibrin [8,19].

In summary, LOCBE induces consumption coagulopathy, depletion of some coagulation factors and inhibitors, and secondary fibrinolysis. It induces a special form of DIC, different from that observed in other clinical situations such as trauma, neoplasia, and sepsis [8,19,28,37,39].
